Conductive sheet, touch panel, display device, method for producing conductive sheet, and recording medium

ABSTRACT

The conductive sheet according to the present invention includes a base and a conductive portion that is formed on at least one main surface of the base and is formed from a plurality of thin metal wires, where a mesh pattern in which different mesh shapes are arrayed in plan view is formed by the conductive portion, and the mesh pattern is configured such that, in a power spectrum of a two-dimensional distribution of centroid positions of the mesh shapes, an average intensity on a higher spatial frequency band side than a predetermined spatial frequency is larger than an average intensity on a lower spatial frequency band side than the predetermined spatial frequency. The conductive sheet can reduce the granular feeling of noise due to pattern which the conductive sheet has and greatly improve the visibility of an object for observation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication PCT/JP2012/075486 filed on Oct. 2, 2012, which claimspriority under 35 U.S.C. 119(a) to Application No. 2011-221432 filed inJapan on Oct. 5, 2011, all of which are hereby expressly incorporated byreference into the present application.

BACKGROUND OF THE INVENTION

The present invention relates to a conductive sheet, a touch panel and adisplay device including the conductive sheet, a method for producingthe conductive sheet, and a recording medium on which a program isrecorded.

In recent years, electronic apparatuses including a touch panel havebecome widely used. The touch panel is mounted in many apparatusesincluding a small-size screen, such as a mobile phone or a personaldigital assistant (PDA). In the future, the mounting of the touch panelin apparatuses including a large-size screen, such as a display for apersonal computer (PC), is adequately expected.

As a conventional touch panel electrode, in terms of opticaltransparency, an indium tin oxide (ITO) is mainly used. It is known thatthe electric resistance per unit area of the ITO is relatively highcompared with those of metals and the like. That is, in the case of theITO, as the size of the screen (total area of the touch panel)increases, the surface resistance of the entire electrode increases. Asa result, since the transmission rate of the current between electrodesis reduced, a problem that the time until the contact position isdetected after touching the touch panel (that is, response speed)increases becomes noticeable.

Therefore, various techniques for reducing the surface resistance byconfiguring electrodes by forming a number of lattices with a thin wire(thin metal wire) that is formed of a metal with low electric resistancehave been proposed (refer to Pamphlet of WO 1995/27334, Pamphlet of WO1997/18508 and JP 2003-099185 A).

Incidentally, when the same mesh shape is regularly arrayed, there is adisadvantage in that moire (interference fringes) is easily generated inrelation to pixels constituting a display screen. Therefore, varioustechniques for improving the visibility of an object for observation byarraying the respective mesh shapes regularly or irregularly to suppressthe granular feeling of noise (also referred to as feeling of roughness)have been proposed.

For example, as shown in FIG. 46A, JP 2009-137455 A ([0029]) discloses awindow for a movable body for riding including a mesh layer 4 and thepattern PT1 of the shape thereof in plan view. In the mesh layer 4, anarc-shaped conductive wire 2 obtained by eliminating a part of thecircle is repeatedly disposed in a lattice shape and the end of thearc-shaped wire 2 is connected near the center of the adjacentarc-shaped wires 2. JP 2009-137455 A describes that not only visibilitybut also the electromagnetic wave shielding property and the resistanceto breakage can be improved thereby.

As shown in FIG. 46B, JP 2009-16700 A ([0022] to [0024]) discloses atransparent conductive substrate produced using a solution that forms amesh-like structure on a substrate naturally when left after beingcoated on one surface of the substrate, that is, a self-organizing metalparticle solution, and the pattern PT2 of the shape thereof in planview. JP 2009-16700 A describes that the irregular mesh-like structure,which does not cause a moire phenomenon, is obtained thereby.

As shown in FIG. 46C, JP 2009-302439 A ([0011] to [0015]) discloses alight-transmissive electromagnetic wave shielding material and thepattern PT3 of the shape thereof in plan view. In the material, anelectromagnetic wave shielding layer 6 has a structure of a sea regionof a sea island structure and the shapes of island regions 8 as openingssurrounded by the electromagnetic wave shielding layer 6 are mutuallydifferent. JP 2009-302439 A describes that thereby, the opticaltransparency and the electromagnetic wave shielding property areimproved without occurrence of moire.

However, when further reducing the granular feeling of noise and improvethe visibility in the patterns PT1 and PT2 disclosed in PatentLiteratures 4 and 5, there is a structural problem of the patterns.

For example, in the mesh-like pattern PT1 disclosed in JP 2009-137455 A,the arc-shaped wire 2 is repeatedly disposed in a lattice shape.Accordingly, the periodicity of the wire 2 is very high. That is, whenthe power spectrum of the pattern PT1 is calculated, it is predictedthat a sharp peak is present in a spatial frequency band correspondingto the inverse of the arrangement interval of the wire 2. Here, in orderto further improve the visibility of the pattern PT1, it is necessary toreduce the size (diameter) of the arc of the wire 2.

In the mesh-like pattern PT2 disclosed in JP 2009-16700 A, the shape orsize of the mesh is irregular, and accordingly, irregularity is veryhigh. That is, when the power spectrum of the pattern PT2 is calculated,it is predicted that an approximately fixed value (close to white noisecharacteristics) is obtained regardless of a spatial frequency band.Here, in order to further improve the visibility of the pattern PT2, itis necessary to reduce the size of self-organization.

Therefore, in both the patterns PT1 and PT2, when further improving thevisibility, there is a disadvantage in that the light transmittance orproductivity is reduced.

Further, the pattern PT3 disclosed in JP 2009-302439 A does not form amesh shape. Accordingly, a variation occurs in the wiring shape of thecut edge. Therefore, when the pattern PT3 is used, for example, as anelectrode, there is a disadvantage in that stable current transmissionperformance is not obtained.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve theabove-described problems, and an object of the present invention is toprovide a conductive sheet, a touch panel, and a display device capableof reducing the granular feeling of noise due to the pattern and capableof significantly improving the visibility of an object for observation,a method for producing the conductive sheet, and a recording medium onwhich a program is recorded.

The conductive sheet according to the present invention includes: abase; and a conductive portion that is formed on at least one mainsurface of the base and is formed from a plurality of thin metal wires,wherein a mesh pattern in which different mesh shapes are arrayed inplan view is formed by the conductive portion, and the mesh pattern isconfigured such that, in a power spectrum of a two-dimensionaldistribution of centroid positions of the mesh shapes, an averageintensity on a higher spatial frequency band side than a predeterminedspatial frequency is larger than an average intensity on a lower spatialfrequency band side than the predetermined spatial frequency.

Preferably, the predetermined spatial frequency is a spatial frequencyat which visual response characteristics of human are equivalent to 5%of a maximum response.

Preferably, the visual response characteristics of human are visualresponse characteristics obtained based on a Dooley-Shaw function at adistance of distinct vision of 300 mm, and the predetermined spatialfrequency is 6 cycles/mm.

Preferably, the predetermined spatial frequency is a spatial frequencyat which a value of the power spectrum is maximized.

Preferably, each of the mesh shapes is a polygonal shape.

Preferably, each of the mesh shapes is determined in accordance with aVoronoi diagram based on a plurality of positions in a planar region.

Preferably, each of the mesh shapes is determined in accordance with aDelaunay diagram based on a plurality of positions in a planar region.

Preferably, in a two-dimensional distribution of the centroid positions,a root mean square deviation of the centroid positions which aredisposed along a predetermined direction with respect to a directionperpendicular to the predetermined direction is equal to or greater than15 μm and equal to or less than 65 μm.

Preferably, the mesh pattern is formed by arraying the mesh shapeswithout a space.

The mesh pattern may include repeated shapes.

Preferably, the conductive portion includes a first conductive portion,which is formed on one main surface of the base and is formed from aplurality of thin metal wires, and a second conductive portion, which isformed on the other main surface of the base and is formed from aplurality of thin metal wires, and the mesh pattern is formed bycombining the first and second conductive portions.

Preferably, the conductive sheet further includes: a first protectivelayer that is provided on the one main surface and covers the firstconductive portion; and a second protective layer that is provided onthe other main surface and covers the second conductive portion, and arelative refractive index of the base with respect to the firstprotective layer and/or a relative refractive index of the base withrespect to the second protective layer are equal to or greater than 0.86and equal to or less than 1.15.

Preferably, the conductive sheet further includes: a first dummyelectrode portion that is formed on the one main surface and is formedfrom a plurality of thin metal wires electrically insulated from thefirst conductive portion, and the first conductive portion includes aplurality of first conductive patterns which are disposed in onedirection and to which a plurality of first sensing portions arerespectively connected, the first dummy electrode portion includes aplurality of first dummy patterns disposed in an opening portion betweenthe first conductive patterns adjacent to each other, and a wiringdensity of the first dummy patterns is equal to a wiring density of thefirst conductive patterns.

Preferably, the conductive portion is formed on one main surface of thebase.

The touch panel according to the present invention includes: theconductive sheet according to any one of the above-described conductivesheets; and a detection control unit that detects a contact position ora proximity position from a main surface side of the conductive sheet.

The display device according to the present invention includes: theconductive sheet according to any one of the above-described conductivesheets; a detection control unit that detects a contact position or aproximity position from the one main surface side of the conductivesheet; and a display unit that displays an image on a display screenbased on a display signal, wherein the conductive sheet is disposed onthe display screen with the other main surface side facing the displayunit.

The method for producing a conductive sheet according to the presentinvention includes: a generation step of generating image datarepresenting a design of a mesh pattern in which different mesh shapesare arrayed; a calculation step of calculating an evaluation value,which quantifies a degree of variation of centroid positions of the meshshapes, based on the generated image data; a determination step ofdetermining a piece of the image data as output image data based on thecalculated evaluation value and predetermined evaluation conditions; andan output step of obtaining a conductive sheet, in which the meshpattern is formed on a base in plan view, by outputting and forming aconductive wire on the base based on the determined output image data.

The program according to the present invention causes a computer tofunction as: an image data generation unit for generating image datarepresenting a design of a mesh pattern in which different mesh shapesare arrayed; an evaluation value calculation unit for calculating anevaluation value, which quantifies a degree of variation of centroidpositions of the mesh shapes, based on the image data generated by theimage data generation unit; and an image data determination unit fordetermining a piece of the image data as output image data based on theevaluation value calculated by the evaluation value calculation unit andpredetermined evaluation conditions.

Preferably, the evaluation value calculation unit calculates theevaluation value based on a power spectrum of a two-dimensionaldistribution of the centroid positions.

Preferably, the evaluation value calculation unit calculates, in atwo-dimensional distribution of the centroid positions, a statisticalvalue of the centroid positions, which are disposed along apredetermined direction, with respect to a direction perpendicular tothe predetermined direction as the evaluation value.

The recording medium according to the present invention is acomputer-readable recording medium that records the program describedabove.

The recording medium according to the present invention is acomputer-readable recording medium that causes a computer to execute asa procedure: a generation step of generating image data representing adesign of a mesh pattern in which different mesh shapes are arrayed; acalculation step of calculating an evaluation value, which quantifies adegree of variation of centroid positions of the mesh shapes, based onthe generated image data; and a determination step of determining apiece of the image data as output image data based on the calculatedevaluation value and predetermined evaluation conditions.

Preferably, in the calculation step, the evaluation value is calculatedbased on a power spectrum of a two-dimensional distribution of thecentroid positions.

Preferably, in the calculation step, in a two-dimensional distributionof the centroid positions, a statistical value of the centroidpositions, which are disposed along a predetermined direction, withrespect to a direction perpendicular to the predetermined direction iscalculated as the evaluation value.

According to the conductive sheet, the touch panel, and the displaydevice of the present invention, the mesh pattern is formed such thatthe average intensity on the side of the higher spatial frequency bandthan the predetermined spatial frequency is larger than the averageintensity on the side of the lower spatial frequency band than thepredetermined spatial frequency in the power spectrum of thetwo-dimensional distribution of the centroid positions of the respectivemesh shapes. Therefore, the amount of noise on the side of the higherspatial frequency band is relatively larger compared with that on theside of the lower spatial frequency band. Since the visual perception ofhuman has a property in which the response characteristics in the lowspatial frequency band are superior, but the response characteristicsabruptly deteriorate in the middle to high spatial frequency bands,feeling of noise that human feels visually is lowered. Accordingly, itis possible to reduce the granular feeling of noise due to pattern whichthe conductive sheet has and to greatly improve the visibility of anobject for observation.

According to the method for producing a conductive sheet and therecording medium on which the program is recorded of the presentinvention, image data representing the design of the mesh pattern inwhich different mesh shapes are arrayed is generated, an evaluationvalue quantifying the degree of variation of the centroid position ofeach of the mesh shapes is calculated based on the image data, and apiece of the image data is determined as output image data based on theevaluation value and predetermined evaluation conditions. Therefore, itis possible to determine each mesh shape having noise characteristicssatisfying the predetermined evaluation conditions. In other words, bycontrolling the pattern shape appropriately, it is possible to reducethe granular feeling of noise and to greatly improve the visibility ofan object for observation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic plan view showing an example of a conductivesheet according to the present embodiment, and FIG. 1B is across-sectional view of the conductive sheet shown in FIG. 1A in which apart of the conductive sheet is omitted.

FIG. 2A is a schematic plan view showing another example of theconductive sheet according to the present embodiment, and FIG. 2B is across-sectional view of the conductive sheet shown in FIG. 2A in which apart of the conductive sheet is omitted.

FIG. 3 is a schematic explanatory diagram showing the pixel arrangementof a display unit.

FIG. 4 is a schematic cross-sectional view of a display device includingthe conductive sheet shown in FIG. 2A.

FIG. 5A is a plan view showing an example of the pattern of a firstconductive portion shown in FIG. 2A, and FIG. 5B is a plan view showingan example of the pattern of a second conductive portion shown in FIG.2A.

FIG. 6 is a partially enlarged plan view of a first sensor portion shownin FIG. 5A.

FIG. 7 is a partially enlarged plan view of a second sensor portionshown in FIG. 5B.

FIG. 8 is a schematic plan view of a conductive sheet in a state wherefirst and second conductive portions are combined.

FIG. 9A is a schematic explanatory diagram showing a result of theselection of eight points from one planar region, FIG. 9B is a schematicexplanatory diagram showing a result of the determination of the wiringshape according to the Voronoi diagram, and FIG. 9C is a schematicexplanatory diagram showing a result of the determination of the wiringshape according to the Delaunay diagram.

FIG. 10A is a schematic explanatory diagram visualizing image datarepresenting the design of the mesh pattern, FIG. 10B is a distributionmap of the power spectrum obtained by performing the FFT on the imagedata shown in FIG. 10A, and FIG. 10C is a cross-sectional view takenalong the line XC-XC of the power spectrum distribution shown in FIG.10B.

FIG. 11 is a graph showing an example of the standard visual responsecharacteristics of human.

FIG. 12 is a cross-sectional view taken along the X axis of the powerspectrum obtained by performing the FFT on the image data of the meshpattern according to the present embodiment and various patternsaccording to conventional examples.

FIG. 13 is an explanatory diagram showing the centroid positions of therespective regions shown in FIG. 9B.

FIG. 14 is a schematic explanatory diagram showing the relationshipbetween the mesh pattern and the centroid position of each mesh shape.

FIG. 15A is a schematic explanatory diagram visualizing the image datarepresenting the centroid position distribution of the mesh shapesincluded in the mesh pattern shown in FIG. 14, FIG. 15B is adistribution map of the power spectrum obtained by performing the FFT onthe centroid image data shown in FIG. 15A, and FIG. 15C is across-sectional view taken along the line XVC-XVC of the power spectrumdistribution map shown in FIG. 15B.

FIG. 16 is a comparison diagram of the graphs shown in FIGS. 10C and15C.

FIGS. 17A and 17B are schematic explanatory diagrams showing thecharacteristics of the centroid spectrum.

FIGS. 18A and 18B are explanatory diagrams schematically showing amethod of calculating the RMS of the respective centroid positions,which are disposed along a predetermined direction, with respect to adirection perpendicular to the predetermined direction.

FIGS. 19A to 19D are schematic explanatory diagrams of examples (firstto third examples) in which other elements are added in a region of anopening that is topologically closed.

FIGS. 20A to 20D are schematic explanatory diagrams of examples (fourthto sixth examples) in which a mesh shape is not formed due to beingtopologically open.

FIG. 21A is a schematic explanatory diagram showing the path of parallellight irradiated toward the thin metal wire, FIG. 21B is a schematicexplanatory diagram showing the path of obliquely incident lightirradiated toward the thin metal wire, and FIG. 21C is a graph showingthe intensity distribution of transmitted light in FIG. 21B.

FIG. 22A is a schematic explanatory diagram showing the path ofobliquely incident light irradiated toward the thin metal wire in theconfiguration according to the present invention, and FIG. 22B is agraph showing the intensity distribution of transmitted light in FIG.22A.

FIG. 23A is a schematic plan view of a first sensor portion according toa reference example, FIG. 23B is a schematic explanatory diagram showingthe path of external light incident on the first sensor portion shown inFIG. 23A, and FIG. 23C is a graph showing the intensity distribution ofreflected light in the first sensor portion shown in FIG. 23A.

FIG. 24A is a schematic explanatory diagram of the first sensor portionaccording to the present embodiment, FIG. 24B is a schematic explanatorydiagram showing the path of external light incident on the first sensorportion shown in FIG. 24A, and FIG. 24C is a graph showing the intensitydistribution of reflected light in the first sensor portion shown inFIG. 24A.

FIG. 25 is a block diagram showing the schematic configuration of amanufacturing apparatus for producing the conductive sheet according tothe present embodiment.

FIG. 26 is a flowchart provided to explain the operation of an imagegeneration apparatus shown in FIG. 25.

FIG. 27 is a flowchart for a method of generating output image data(step S2 of FIG. 26).

FIG. 28A is an explanatory diagram showing the definition of the pixeladdress in image data, and FIG. 28B is an explanatory diagram showingthe definition of the pixel value in image data.

FIG. 29A is a schematic diagram of the initial positions of seed points,and FIG. 29B is a Voronoi diagram based on the seed points shown in FIG.29A.

FIG. 30 is a schematic explanatory diagram showing a method ofdetermining a design (wiring shape) at the end of a unit region.

FIG. 31 is a schematic explanatory diagram showing a result when imagedata is generated by arraying unit image data regularly.

FIG. 32 is a flowchart showing the detail of step S26 shown in FIG. 27,

FIG. 33A is an explanatory diagram showing the positional relationshipof first seed points, second seed points and candidate points in animage region, and FIG. 33B is an explanatory diagram showing a resultwhen the position of the seed point is updated by exchanging the secondseed point for the candidate point.

FIG. 34A is a schematic explanatory diagram showing a result of thecutting of a first conductive pattern and a first dummy pattern, andFIG. 34B is a schematic explanatory diagram showing a result of thecutting of a second conductive pattern.

FIG. 35 is a flowchart showing a method of producing a conductive sheetaccording to the present embodiment.

FIG. 36A is a cross-sectional view showing the produced photosensitivematerial in which a part thereof is omitted, and FIG. 36B is a schematicexplanatory diagram showing double-sided simultaneous exposure to thephotosensitive material.

FIG. 37 is a schematic explanatory diagram showing the execution stateof first exposure processing and second exposure processing.

FIG. 38 is a schematic cross-sectional view of a touch panel accordingto a first modification.

FIG. 39A is a partially enlarged plan view of a first sensor portionshown in FIG. 38, and FIG. 39B is a partially enlarged plan view of asecond sensor portion shown in FIG. 38.

FIG. 40 is a front view of the touch panel shown in FIG. 38 in which apart of the touch panel is omitted.

FIG. 41A is a partially enlarged plan view of a first sensor portionaccording to a second modification, and FIG. 41B is a partially enlargedplan view of a second sensor portion according to the secondmodification.

FIG. 42 is a cross-sectional view of a conductive sheet according to athird modification in which a part of the conductive sheet is omitted.

FIG. 43 is a cross-sectional view of a conductive sheet according to afourth modification in which a part of the conductive sheet is omitted.

FIG. 44 is a partially enlarged plan view of a conductive sheetaccording to a fifth modification.

FIG. 45 is an explanatory diagram showing a result of sensory evaluationaccording to the present embodiment.

FIGS. 46A to 46C are enlarged plan views of the pattern according tocomparative examples.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a preferred embodiment of a conductive sheet according tothe present invention will be described in detail in relation to a touchpanel and a display device in which the conductive sheet is used andwith reference to the accompanying diagrams. In the presentspecification, the term “to” is used to represent a numerical range, andthis means a numerical range including the numerical values describedbefore and after “to” as lower and upper limits.

The Present Embodiment

As shown in FIGS. 1A and 1B, a conductive sheet 10 according to thepresent embodiment includes a transparent base 12 (base). Thetransparent base 12 having insulation properties and high translucencyis formed of a material such as a resin, a glass, and silicon. Asexamples of the resin, polyethylene terephthalate (PET), polymethylmethacrylate (PMMA), polypropylene (PP), polystyrene (PS), and the likecan be mentioned.

A first conductive portion 14 a and a first dummy electrode portion 15 a(refer to FIGS. 2A and 2B) are formed on one main surface (arrow s1direction side in FIG. 1B) of the transparent base 12. The firstconductive portion 14 a and the first dummy electrode portion 15 a havea mesh pattern 20 formed by a thin wire made of metal (hereinafter,referred to as a thin metal wire 16 and also referred to as thin metalwire 16 p, 16 q, 16 r, or 16 s in some cases) and an opening 18. Thethin metal wire 16 is made of gold (Au), silver (Ag), or copper (Cu),for example. The line width of the thin metal wire 16 can be selectedfrom 30 μm or less.

Specifically, the first conductive portion 14 a and the first dummyelectrode portion 15 a have the mesh pattern 20 in which different meshshapes 22 are arrayed without any space. In other words, the meshpattern 20 is a random pattern with no regularity (uniformity) for eachmesh shape 22. For example, the hatched mesh shape 22 in the meshpattern 20 is a quadrangular shape, and is formed by a thin metal wire16 p linearly connecting the apices C1 and C2 to each other, a thinmetal wire 16 q linearly connecting the apices C2 and C3 to each other,a thin metal wire 16 r linearly connecting the apices C3 and C4 to eachother, and a thin metal wire 16 s linearly connecting the apices C4 andC1 to each other. As is understood from FIG. 1B, all of the mesh shapes22 are polygonal shapes having at least three sides.

The “polygon” hereinafter described in this specification includes notonly a geometrically perfect polygon but also a “substantial polygon” inwhich the above perfect polygon is slightly changed. As examples of theslight change, addition of a point element and a line element that aresmall compared with the mesh shape 22, partial defect of each side (thinmetal wire 16) that forms the mesh shape 22, and the like can bementioned.

A first protective layer 26 a is bonded to approximately the entiresurface of the first conductive portion 14 a with a first adhesive layer24 a interposed therebetween so as to cover the thin metal wire 16. Asmaterials of the first adhesive layer 24 a, a wet lamination adhesive, adry laminate adhesive, a hot melt adhesive, or the like can bementioned.

Similarly to the transparent base 12, the first protective layer 26 a isformed of a material having high translucency, such as a resin, a glass,and silicon. The refractive index n1 of the first protective layer 26 ais a value that is equal to or close to the refractive index n0 of thetransparent base 12. In this case, the relative refractive index nr1 ofthe transparent base 12 with respect to the first protective layer 26 ais a value close to 1.

Here, the refractive index in this specification means a refractiveindex for light with a wavelength of 589.3 nm (D line of sodium). Forexample, in regard to resins, the refractive index is defined by ISO14782: 1999 (corresponding to JIS K 7105) that is an internationalstandard. In addition, the relative refractive index nr1 of thetransparent base 12 with respect to the first protective layer 26 a isdefined as nr1=(n1/n0). Here, it is preferable that the relativerefractive index nr1 be in a range of 0.86 or more and 1.15 or less, anda range of 0.91 or more and 1.08 or less is more preferable.

The conductive sheet 10 is used as electrodes for various devices suchas an inorganic EL device, an organic EL device, or a solar cell, forexample. Other than the application to electrodes, the conductive sheet10 can also be applied to a transparent heating element that generatesheat when a current is caused to flow (for example, a defroster of avehicle) and an electromagnetic shielding material to blockelectromagnetic waves.

In a conductive sheet 11 according to the present embodiment, as shownin FIGS. 2A and 2B, not only the first conductive portion 14 a but alsothe first dummy electrode portion 15 a is formed on one main surface(arrow s1 direction side in FIG. 2B) of the transparent base 12. Thefirst conductive portion 14 a and the first dummy electrode portion 15 ahas the mesh pattern 20 formed by the thin metal wire 16 and the opening18. In the conductive sheet 11 applied to the touch panel, the linewidth of the thin metal wire 16 is preferably in the range of 0.1 μm ormore and 1.5 μm or less, more preferably in the range of 1 μm or moreand 9 μm or less, and even more preferably in the range of 2 μm or moreand 7 μm or less.

Here, the first dummy electrode portion 15 a is disposed so as to bespaced apart from the first conductive portion 14 a by a predetermineddistance. That is, the first dummy electrode portion 15 a is in a statewhere it is electrically insulated from the first conductive portion 14a. The first protective layer 26 a is bonded to approximately the entiresurfaces of the first conductive portion 14 a and the first dummyelectrode portion 15 a via the first adhesive layer 24 a so as to coverthe thin metal wire 16.

Hereinafter, the respective portions (including the first conductiveportion 14 a, the first dummy electrode portion 15 a, the first adhesivelayer 24 a, and the first protective layer 26 a) formed on the one mainsurface (arrow s1 direction side in FIGS. 1B and 2B) of the transparentbase 12 is collectively referred to as a first laminate portion 28 a insome cases.

A second conductive portion 14 b is formed on the other main surface(arrow s2 direction side in FIG. 2B) of the transparent base 12.Similarly to the first conductive portion 14 a, the second conductiveportion 14 b has the mesh pattern 20 formed by the thin metal wire 16and the opening 18. The transparent base 12 is formed of an insulatingmaterial, and the second conductive portion 14 b is in a state where itis electrically insulated from the first conductive portion 14 a and thefirst dummy electrode portion 15 a.

A second protective layer 26 b is bonded to approximately the entiresurface of the second conductive portion 14 b with a second adhesivelayer 24 b interposed therebetween so as to cover the thin metal wire16. The material of the second adhesive layer 24 b may be the same asthat of the first adhesive layer 24 a, or may be different from that ofthe first adhesive layer 24 a. The material of the second protectivelayer 26 b may be the same as that of the first protective layer 26 a,or may be different from that of the first protective layer 26 a.

The refractive index n2 of the second protective layer 26 b is a valuethat is equal to or close to the refractive index n0 of the transparentbase 12. In this case, the relative refractive index nr2 of thetransparent base 12 with respect to the second protective layer 26 b isa value close to 1. Here, the definitions of the refractive index andthe relative refractive index are as described above. The relativerefractive index nr2 of the transparent base 12 with respect to thesecond protective layer 26 b is defined as nr2=(n2/n0). Here, it ispreferable that the relative refractive index nr2 be in a range of 0.86or more and 1.15 or less, and a range of 0.91 or more and 1.08 or lessis more preferable.

Hereinafter, the respective portions (including the second conductiveportion 14 b, the second adhesive layer 24 b, and the second protectivelayer 26 b) formed on the other main surface (arrow s2 direction side inFIG. 2B) of the transparent base 12 is collectively referred to as asecond laminate portion 28 b in some cases.

The conductive sheet 11 is applied to a touch panel of a display unit 30(display unit), for example. The display unit 30 may be formed of aliquid crystal panel, a plasma panel, an organic electro-luminescence(EL) panel, an inorganic EL panel, and the like.

As shown in FIG. 3 in which a part thereof is omitted, the display unit30 is constituted by arraying a plurality of pixels 32 in a matrix form.One pixel 32 is formed by arraying three subpixels (a red subpixel 32 r,a green subpixel 32 g, and a blue subpixel 32 b) in a horizontaldirection. Each subpixel has a rectangular shape that is long in avertical direction. The arrangement pitch of the pixels 32 in thehorizontal direction (horizontal pixel pitch Ph) and the arrangementpitch of the pixels 32 in the vertical direction (vertical pixel pitchPv) are approximately the same. That is, a shape (refer to a shadedregion 36) including one pixel 32 and a black matrix 34 (light blockingmaterial) surrounding the one pixel 32 is a square. In addition, theaspect ratio of one pixel 32 is not 1, and the horizontal length islarger than the vertical length. When the conductive sheet 10 isdisposed on the display panel of the display unit 30 having the pixelarrangement described above, there is almost no interference of thespatial frequency between the arrangement period of the pixels 32 andthe thin metal wire 16 formed at random, and thus the generation ofmoire is suppressed.

Next, a display device 40 including the conductive sheet 11 according tothe present embodiment will be described with reference to FIGS. 4 to 8.Here, a projected capacitive touch panel will be described as anexample.

As shown in FIG. 4, the display device 40 includes the display unit 30(refer to FIG. 3) that can display a color image and/or a monochromeimage, a touch panel 44 that detects a contact position from an inputscreen 42 (arrow Z1 direction side), and a housing 46 in which thedisplay unit 30 and the touch panel 44 are housed. The user can accessthe touch panel 44 through a large opening provided on the surface(arrow Z1 direction side) of the housing 46.

The touch panel 44 includes not only the conductive sheet 11 (refer toFIGS. 2A and 2B) described above but also a cover member 48 laminated onthe surface (arrow Z1 direction side) of the conductive sheet 11, aflexible substrate 52 electrically connected to the conductive sheet 11through a cable 50, and a detection control unit 54 disposed on theflexible substrate 52.

The conductive sheet 11 is bonded to the surface (arrow Z1 directionside) of the display unit 30 through an adhesive layer 56. Theconductive sheet 11 is disposed on the display screen such that theother main surface side (second conductive portion 14 b side) faces thedisplay unit 30.

The cover member 48 functions as the input screen 42 by covering thesurface of the conductive sheet 11. In addition, by preventing directcontact of a contact body 58 (for example, a finger or a stylus pen), itis possible to suppress the occurrence of a scratch, adhesion of dust,and the like, and thus it is possible to stabilize the conductivity ofthe conductive sheet 11.

For example, the material of the cover member 48 may be a glass or aresin film. One surface (arrow Z2 direction side) of the cover member 48may be coated with silicon oxide or the like and be bonded to onesurface (arrow Z1 direction side) of the conductive sheet 11. In orderto prevent damage due to rubbing or the like, the conductive sheet 11and the cover member 48 may be pasted together.

The flexible substrate 52 is an electronic substrate having flexibility.In the example shown in this diagram, the flexible substrate 52 is fixedto the inner wall of the side surface of the housing 46, but theposition fixedly set up may be changed in various ways. The detectioncontrol unit 54 constitutes an electronic circuit that catches a changein the capacitance between the contact body 58 and the conductive sheet11 and detects the contact position (or the proximity position) when thecontact body 58 that is a conductor is brought into contact with (orcomes close to) the input screen 42.

As shown in FIG. 5A, a first sensor portion 60 a, which is disposed inthe display region of the display unit 30 (refer to FIGS. 3 and 4), anda first terminal wiring portion 62 a (so-called frame), which isdisposed in the outer peripheral region of the display region, areprovided on one main surface of the conductive sheet 11 in plan view inthe arrow Z2 direction.

The external shape of the conductive sheet 11 in plan view is arectangular, and the external shape of the first sensor portion 60 a isalso a rectangular. In a peripheral portion of the first terminal wiringportion 62 a on one side of the conductive sheet 11 parallel to thearrow Y direction, a plurality of first terminals 64 a are formed in acentral portion in the longitudinal direction so as to be arrayed in thearrow Y direction. A plurality of first connection portions 66 a arearrayed in approximately one row along one side (side parallel to thearrow Y direction in the example shown in this diagram) of the firstsensor portion 60 a. A first terminal wiring pattern 68 a derived fromeach of the first connection portions 66 a is drawn toward the firstterminal 64 a in the outer peripheral region of the display regiondescribed above, and is electrically connected to the correspondingfirst terminal 64 a.

In a portion corresponding to the first sensor portion 60 a, two or morefirst conductive patterns 70 a (mesh pattern) formed by a plurality ofthin metal wires 16 (refer to FIGS. 2A and 2B) are provided. The firstconductive pattern 70 a extends in the arrow X direction (firstdirection), and is arrayed in the arrow Y direction (second direction)perpendicular to the arrow X direction. In addition, each of the firstconductive patterns 70 a is formed by connecting two or more firstsensing portions 72 a in series to each other in the arrow X direction.The respective first sensing portions 72 a, each of which has a contourof almost a rhombic shape, have the same contour shape. Between thefirst sensing portions 72 a adjacent to each other, a first connectionportion 74 a that electrically connects the first sensing portions 72 ato each other is formed. More specifically, an apex angle portion of onefirst sensing portion 72 a is connected to an apex angle portion ofanother first sensing portion 72 a, which is adjacent to the one firstsensing portion 72 a described above in the arrow X direction, throughthe first connection portion 74 a.

At one end side of the first conductive pattern 70 a, the firstconnection portion 74 a is not formed at the open end of the firstsensing portion 72 a. At the other end side of the first conductivepattern 70 a, the first connection portion 66 a is provided at the endof the first sensing portion 72 a. Then, the first conductive pattern 70a is electrically connected to the first terminal wiring pattern 68 athrough the first connection portion 66 a.

In a portion corresponding to the first sensor portion 60 a, two or morefirst dummy patterns 76 a (mesh pattern) formed by a plurality of thinmetal wires 16 (refer to FIGS. 2A and 2B) are provided. Each of thefirst dummy patterns 76 a is disposed in a first opening portion 75 a(refer to FIG. 6) between the adjacent first conductive patterns 70 a.The first dummy pattern 76 a having a contour of almost a rhombic shapeis disposed so as to be spaced apart from the first conductive pattern70 a (the first sensing portion 72 a and the first connection portion 74a) by a predetermined distance. This distance (width) is very smallcompared with the length of one side of the first sensing portion 72 a.Therefore, the thin metal, wires 16 are wired in an approximatelyuniform density on the entire surface of the first sensor portion 60 a.

For convenience of explanation, in FIG. 6, each mesh shape is shown indetail for only one first dummy pattern 76 a (middle right portion ofthe diagram). The contours of the other first dummy patterns 76 a areshown by a dotted line, and the shape of the inside thereof is omitted.

As shown in FIG. 6, each of the first sensing portions 72 a and each ofthe first dummy patterns 76 a are formed by combining two or more firstmesh elements 78 a. Similarly to the mesh shape 22 (refer to FIG. 2B)described above, the shape of the first mesh element 78 a is a polygonalshape having at least three sides. In addition, the first connectionportion 74 a that connects the adjacent first sensing portions 72 a toeach other is formed by at least one first mesh element 78 a.

The first mesh element 78 a that forms a peripheral portion of each ofthe first sensing portions 72 a and each of the first dummy patterns 76a may be a topologically closed space or a topologically open space.This is the same for the first connection portion 74 a.

Further, between the adjacent first conductive patterns 70 a, a firstinsulation portion 80 a that is electrically insulated is disposed.

Here, the wiring density of the first dummy pattern 76 a is equal to thewiring density of the first conductive pattern 70 a (the first sensingportion 72 a and the first connection portion 74 a). In this case, thelight reflectance in the planar region of the first dummy pattern 76 aagrees with the light reflectance in the planar region of the firstconductive pattern 70 a. This is because there is a high correlationbetween the wiring density and the light reflectance when the line widthof the thin metal wire 16 is fixed.

In this description, the wording of “wiring densities are equal” is aconcept including not only the case where the wiring densities arecompletely equal but also the case where the wiring densities aresubstantially equal (the density ratio is in a range of approximately0.8 to 1.2). That is, the difference in light reflectance has only to bea degree that cannot be detected by the visual perception of human(viewer). Further, the measurement area of the wiring density of thethin metal wire 16 has only to be equal to or greater than 1 mm inconsideration of the measurement accuracy and the like.

In addition, the distance between the first conductive pattern 70 a andthe first dummy pattern 76 a may be fixed regardless of the position(“approximately fixed” is also included). This is preferable since thewiring density of the thin metal wire 16 becomes almost uniform.

Further, it is preferable that the coverage (arrangement ratio) of thefirst dummy pattern 76 a with respect to the first opening portion 75 abe in a range of approximately 30% to 95%, and a range of 70% to 95% ismore preferable.

Moreover, the contour of the first dummy pattern 76 a can be variousshapes including a triangle, a rectangle, and a circle. For example, thecontour of the first dummy pattern 76 a may be the same as or similar tothe contour shape of the first sensing portion 72 a (approximatelyrhombic shape in the example shown in FIG. 5A).

On the other hand, as shown in FIG. 5B, a second sensor portion 60 b,which is disposed in the display region of the display unit 30 (refer toFIGS. 3 and 4), and a second terminal wiring portion 62 b (so-calledframe), which is disposed in the outer peripheral region of the displayregion, are provided on the other main surface of the conductive sheet11 in plan view in the arrow Z1 direction.

The external shape of the conductive sheet 11 in plan view is arectangular, and the external shape of the second sensor portion 60 b isalso a rectangular. In a peripheral portion of the second terminalwiring portion 62 b on one side of the conductive sheet 11 parallel tothe arrow Y direction, a plurality of second terminals 64 b are formedin a central portion in the longitudinal direction so as to be arrayedin the arrow Y direction. A plurality of second connection portions 66 b(for example, odd-numbered second connection portions 66 b) are arrayedin approximately one row along one side (side parallel to the arrow Xdirection in the example shown in this diagram) of the second sensorportion 60 b. A plurality of second connection portions 66 b (forexample, even-numbered second connection portions 66 b) are arrayed inapproximately one row along the other side (opposite side to the sidedescribed above) of the second sensor portion 60 b. A second terminalwiring pattern 68 b derived from each of the second connection portions66 b is drawn toward the second terminal 64 b in the outer peripheralregion of the display region described above, and is electricallyconnected to the corresponding second terminal 64 b.

In a portion corresponding to the second sensor portion 60 b, two ormore second conductive patterns 70 b (mesh pattern) formed by aplurality of thin metal wires 16 (refer to FIGS. 2A and 2B) areprovided. The second conductive pattern 70 b extends in the arrow Ydirection (second direction), and is arrayed in the arrow X direction(first direction) perpendicular to the arrow Y direction. In addition,each of the second conductive patterns 70 b is formed by connecting twoor more second sensing portions 72 b in series to each other in thearrow Y direction. The respective second sensing portions 72 b, each ofwhich has a contour of almost a rhombic shape, have the same contourshape. Between the second sensing portions 72 b adjacent to each other,a second connection portion 74 b that electrically connects the secondsensing portions 72 b to each other is formed. More specifically, anapex angle portion of one second sensing portion 72 b is connected to anapex angle portion of another second sensing portion 72 b, which isadjacent to the one second sensing portion 72 b described above in thearrow Y direction, through the second connection portion 74 b.

At one end side of the second conductive pattern 70 b, the secondconnection portion 74 b is not formed at the open end of the secondsensing portion 72 b. At the other end side of the second conductivepattern 70 b, the second connection portion 66 b is provided at the endof the second sensing portion 72 b. Then, the second conductive pattern70 b is electrically connected to the second terminal wiring pattern 68b through the second connection portion 66 b.

In addition, in the second sensor portion 60 b, unlike the first sensorportion 60 a (refer to FIGS. 5A and 6), no dummy pattern is disposed ina second opening portion 75 b between the adjacent second conductivepatterns 70 b.

As shown in FIG. 7, each of second sensing portions 72 b is formed bycombining two or more second mesh elements 78 b. Similarly to the meshshape 22 (refer to FIG. 2A) described above, the shape of the secondmesh element 78 b is a polygonal shape having at least three sides. Thesecond connection portion 74 b that connects the adjacent second sensingportions 72 a to each other is formed by at least one second meshelement 78 b.

In addition, the second mesh element 78 b that forms a peripheralportion of the second sensing portion 72 b may be a topologically closedspace or a topologically open space. This is the same for the secondconnection portion 74 b.

Further, between the adjacent second conductive patterns 70 b, a secondinsulation portion 80 b that is electrically insulated is disposed.

As shown in FIG. 8, the second conductive pattern 70 b formed on theother surface (arrow Z2 direction side) is arrayed such that an opening(a part of the first opening portion 75 a) between the first conductivepattern 70 a and the first dummy pattern 76 a formed on the one surface(arrow Z1 direction side) is embedded in plan view of the conductivesheet 11. In addition, in a planar region where the contour of the firstconductive pattern 70 a and the contour of the second conductive pattern70 b overlap each other, the positions of the thin metal wires 16 ofboth the first and second conductive patterns 70 a and 70 b completelymatch each other. Further, in a planar region where the contour of thefirst dummy pattern 76 a and the contour of the second conductivepattern 70 b overlap each other, the positions of the thin metal wires16 of both the first dummy pattern 76 a and the second conductivepattern 70 b completely match each other. As a result, the entiresurface of the conductive sheet 11 is filled with a number of polygons82 (mesh shapes) in plan view of the conductive sheet 11.

It is preferable that the length of one side of the first sensingportion 72 a (and the second sensing portion 72 b) be 3 mm to 10 mm, and4 mm to 6 mm is more preferable. When the conductive sheet 11 is appliedto the touch panel, if the length of one side is less than the lowerlimit described above, the capacitance of the first sensing portion 72 a(and the second sensing portion 72 b) at the time of detection isreduced, and accordingly, a possibility of detection failure isincreased. On the other hand, if the length of one side exceeds theupper limit described above, there is a possibility that the detectionaccuracy of the contact position will be reduced. From the same point ofview, as described above, it is preferable that the average length ofone side of the polygon 82 (first and second mesh elements 78 a and 78b) be 100 μm to 400 μm, 150 μm to 300 μm is more preferable, and 210 μmto 250 μm is most preferable. When one side of the polygon 82 is in therange described above, it is also possible to maintain the transparencymore satisfactorily. Accordingly, when the conductive sheet 11 isattached to the front surface of the display unit 30, it is possible toview the display without uncomfortable feeling.

Referring back to FIG. 6, it is preferable that the width w1 of thefirst connection portion 74 a be 0.2 mm to 1.0 mm, and 0.4 mm to 0.8 mmis more preferable. When w1 is less than the lower limit describedabove, the number of wiring lines for connecting the first sensingportions 72 a is reduced, and accordingly, the resistance betweenelectrodes is increased. On the other hand, when w1 exceeds the upperlimit described above, the overlapping area between the first and secondsensing portions 72 a and 72 b is increased, and accordingly, the amountof noise is increased. The same is true regarding the width of thesecond connection portion 74 b (refer to FIG. 7).

It is preferable that the separation width w2 between the first andsecond sensing portions 72 a and 72 b be 0.1 mm to 0.6 mm, and 0.2 mm to0.5 mm is more preferable. When w2 is less than the lower limitdescribed above, the variation in capacitance due to the contact (or theproximity) of the contact body 58 is reduced, and accordingly, theamount of signal is reduced. On the other hand, when w2 exceeds theupper limit described above, the density of the first sensing portions72 a is reduced, and accordingly, the resolution of the sensor isreduced.

Subsequently, an example of a method of determining the wiring shapes ofthe first conductive portion 14 a, the first dummy electrode portion 15a, and the second conductive portion 14 b will be described withreference to FIGS. 9A to 9C.

In the present embodiment, the mesh pattern 20 is determined from aplurality of positions that exist in one planar region 100. As shown inFIG. 9A, it is assumed that eight seed points P₁ to P₈ are randomlyselected from the square planar region 100.

FIG. 9B is a schematic explanatory diagram showing a result of thedetermination of the wiring shape according to the Voronoi diagram(Voronoi tessellation method). In this way, eight regions V₁ to V₈surrounding the eight seed points P₁ to P₈ are determined. Here, theregion V_(i) (i=1 to 8) divided by the Voronoi diagram indicates anaggregate of points that are points to which the seed point P_(i) isclosest. Here, the Euclidean distance is used as a distance function,but it is possible to use various functions.

FIG. 9C is a schematic explanatory diagram showing a result of thedetermination of the wiring shape according to the Delaunay diagram(Delaunay triangulation method). The Delaunay triangulation method is amethod of determining a triangular region by connecting the adjacentpoints among the seed points P₁ to P₈. By the method, the eight regionsV₁ to V₈ having the eight seed points P₁ to P₈ as the apices aredetermined.

In this manner, a wiring shape having the thin metal wire 16 as eachboundary line shown in FIG. 9B (or FIG. 9C) and the opening 18 as eachregion V_(i), that is, each mesh shape 22 when the first conductiveportion 14 a, the first dummy electrode portion 15 a, and the secondconductive portion 14 b overlap each other is determined.

Subsequently, an evaluation value quantifying the noise characteristics(for example, granular noise) of the conductive sheets 10 and 11according to the present invention will be described in detail withreference to FIGS. 10A to 18B. In order to mathematically evaluate thewiring shape of the mesh pattern 20, it is necessary to acquire imagedata to visualize the design of the mesh pattern 20 in advance. Thisimage data Img may be color value data of the conductive sheets 10 and11 read using an input device such as a scanner, or may be image datathat is actually used in forming the output of the mesh pattern 20. Inany case, it is preferable that the image data Img have a highresolution (small pixel size) that can express the average line width ofthe thin metal wire 16 with one or more pixels.

[First Evaluation Value]

A first evaluation value EV1 is an index that quantifies predeterminedphysical characteristics on the basis of a two-dimensional powerspectrum at the centroid position of the mesh shape 22. Hereinafter, thefirst evaluation value EV1 will be described with reference to FIGS. 10Ato 17B.

FIG. 10A is a schematic explanatory diagram visualizing the image dataImg representing the design of the mesh pattern 20. First, a Fouriertransformation (for example, fast Fourier transformation; FFT) isperformed on the image data Img. Accordingly, the shape of the meshpattern 20 can be grasped not as a partial shape but as an overalltendency (spatial frequency distribution).

FIG. 10B is a distribution map of the two-dimensional power spectrum(hereinafter, simply referred to as a spectrum Spc) obtained byperforming the FFT on the image data Img shown in FIG. 10A. Here, thehorizontal axis of the distribution map indicates a spatial frequencywith respect to the X-axis direction, and the vertical axis thereofindicates a spatial frequency with respect to the Y-axis direction. Inaddition, the intensity level (value of the spectrum) decreases as thedisplay density of each spatial frequency band decreases, and theintensity level increases as the display density increases. In theexample of this diagram, the distribution of the spectrum Spc isisotropic and has two circular peaks.

FIG. 10C is a cross-sectional view taken along the line XC-XC of thedistribution of the spectrum Spc shown in FIG. 10B. Since the spectrumSpc is isotropic, FIG. 10C is equivalent to the radial distribution forall angular directions. As is understood from this diagram, the spectrumSpc has so-called band-pass type characteristics in which the intensitylevels in the low spatial frequency band and the high spatial frequencyband are low and the intensity level is high only in the middle spatialfrequency band. That is, according to the terminology of the imageengineering, the image data Img shown in FIG. 10A can be said torepresent a design having the characteristics of “green noise”.

FIG. 11 is a graph showing an example of the standard visual responsecharacteristics of human.

In the present embodiment, the Dooley-Shaw function at the viewingdistance of 300 mm under the distinct vision state is used as thestandard visual response characteristics of human. The Dooley-Shawfunction is a kind of visual transfer function (VTF), and is a typicalfunction imitating the standard visual response characteristics ofhuman. Specifically, this is equivalent to the square value of thecontrast ratio characteristic of brightness. The horizontal axis of thegraph is a spatial frequency (unit: cycle/mm), and the vertical axisthereof is a value of the VTF (unit: no dimension).

Assuming that the viewing distance is 300 mm, the value of the VTF isfixed (equal to 1) in the range of 0 to 1.0 cycle/mm, and the value ofthe VTF tends to decrease gradually as the spatial frequency increases.That is, this function functions as a low pass filter to cut off themiddle to high spatial frequency bands.

FIG. 12 is a cross-sectional view taken along the X axis of the spectrumSpc obtained by performing the FFT on the image data Img representingthe designs of the mesh pattern 20 according to the present embodimentand various patterns PT1 to PT3 according to conventional examples.

The spectrum Spc of the pattern PT1 shown in FIG. 46A has a wide peak(range of 2 cycles/mm to 30 cycles/mm) having about 10 cycles/mm as theapex. In addition, the spectrum Spc of the pattern PT2 shown in FIG. 46Bhas a wide peak (range of 3 cycles/mm to 20 cycles/mm) having about 3cycles/mm as the center. Further, the spectrum Spc of the pattern PT3shown in FIG. 46C has a slightly narrow peak (range of 8 cycles/mm to 18cycles/mm) having about 10 cycles/mm as the center. In contrast, thespectrum Spc of the mesh pattern 20 (written as M in this diagram; thesame in FIG. 16 described hereinafter) has a narrow peak having about8.8 cycles/mm as the center.

The relationship between the characteristics of the spectrum Spc shownin FIG. 10C and the centroid position of each mesh shape 22 will bedescribed below. As shown in FIG. 13, it is assumed that, for the sameplanar region 100 as in FIG. 3B, the polygonal regions V₁ to V₈ aredetermined using the Voronoi diagram described above. In addition,respective points C₁ to C₈ included in the regions V₁ to V₈ indicate thegeometric position of the centroid of each region.

FIG. 14 is a schematic explanatory diagram showing the relationshipbetween the mesh pattern 20 according to the present embodiment and thecentroid position of each mesh shape 22.

FIG. 15A is a schematic explanatory diagram visualizing image data(hereinafter, referred to as “centroid image data Imgc”) representingthe two-dimensional distribution of the centroid position (hereinafter,referred to as centroid position distribution C) of the respective meshshapes 22 included in the mesh pattern 20 shown in FIG. 14. As isunderstood from this diagram, the centroid position distribution C isappropriately dispersed without the respective centroid positionsoverlapping each other.

FIG. 15B is a distribution map of the two-dimensional power spectrum(hereinafter, simply referred to as a centroid spectrum Spcc) obtainedby performing the FFT on the centroid image data Imgc shown in FIG. 15A.Here, the horizontal axis of the distribution map indicates a spatialfrequency with respect to the X-axis direction, and the vertical axisthereof indicates a spatial frequency with respect to the Y-axisdirection. In addition, the intensity level (value of the spectrum)decreases as the display density of each spatial frequency banddecreases, and the intensity level increases as the display densityincreases. In the example of this diagram, the distribution of thecentroid spectrum Spcc is isotropic and has one circular peak.

FIG. 15C is a cross-sectional view taken along the line XVC-XVC of thedistribution of the centroid spectrum Spcc shown in FIG. 15B. Since thecentroid spectrum Spcc is isotropic, FIG. 15C is equivalent to theradial distribution for all angular directions. As is understood fromthis diagram, the intensity level in the low spatial frequency band islow, and a peak width in the middle spatial frequency band is large.Further, the centroid spectrum Spcc has so-called high-pass typecharacteristics in which the intensity level in the high spatialfrequency band is high compared with that in the low spatial frequencyband. That is, according to the terminology of the image engineering,the centroid image data Imgc shown in FIG. 15A can be said to representa design having the characteristics of “blue noise”.

The power spectrum of the centroid position distribution C in theconductive sheets 10 and 11 can be acquired by the following process.First, the image data Img representing the design of the mesh pattern 20is acquired, each mesh shape 22 (closed space) is identified, thecentroid position (for example, dot of one pixel) is calculated toobtain the centroid image data Imgc, and then, the two-dimensional powerspectrum is calculated. Thereby, the power spectrum (centroid spectrumSpcc) of the centroid position distribution C is obtained.

FIG. 16 is a comparison diagram of the graphs shown in FIGS. 10C and15C. Specifically, the spectrum Spc of the mesh pattern 20 is comparedwith the centroid spectrum Spcc of the centroid position distribution C.For convenience, the intensities of the spectrum Spc and the centroidspectrum Spcc are normalized so that the values of the maximum peaks Pkare equal.

According to this diagram, the peaks Pk have the same spatial frequencyFp, and the value thereof is equivalent to 8.8 cycles/mm. In the highspatial frequency band exceeding the spatial frequency Fp, the intensityof the spectrum Spc decreases gradually, while the intensity of thecentroid spectrum Spcc still maintains a high value. The reason ispresumably that the components of the mesh pattern 20 are line segments,each of which has a predetermined width and which cross each other, andin contrast, the components of the centroid position distribution C arepoints.

FIG. 17A is a schematic explanatory diagram showing the characteristicsof the centroid spectrum Spcc shown in FIG. 15C. The value of thecentroid spectrum Spcc increases gradually in the range of 0 to 5cycles/mm, increases abruptly around 6 cycles/mm, and has a wide peak atabout 10 cycles/mm. Then, the value of the centroid spectrum Spccdecreases gradually in the range of 1.0 to 15 cycles/mm, and a highvalue is maintained in the high spatial frequency band exceeding 15cycles/mm.

Here, a reference spatial frequency Fb (a predetermined spatialfrequency) is set to 6 cycles/mm. The average intensity (average value)of the centroid spectrum Spcc at the lower spatial frequency band sidethan Fb, that is, in the range of 0 to Fb [cycle/mm] is assumed to beP_(L). The average intensity (average value) of the centroid spectrumSpcc at the higher spatial frequency band side than Fb, that is, in therange of Fb [cycle/mm] to Nyquist frequency is assumed to be P_(H).Thus, P_(H) is larger than P_(L). Since the centroid spectrum Spcc hassuch features, the feeling of noise that the viewer visually feels isreduced. The basis thereof is as follows.

For example, the value of Pb is set to be a spatial frequency at whichthe visual response characteristics of human are equivalent to 5% of themaximum response. This is because this intensity level is a level atwhich visual recognition is difficult. In addition, as shown in FIG. 11,the visual response characteristics obtained on the basis of theDooley-Shaw function at the viewing distance of 300 mm are used. This isbecause this function is well suited to the visual responsecharacteristics of human.

That is, the spatial frequency of 6 cycle/mm equivalent to 5% of themaximum response in the Dooley-Shaw function at the distance of distinctvision of 300 mm can be used as the value of Fb. The spatial frequencyof 6 cycles/mm is equivalent to a spacing of 1.67 μm.

In addition, as shown in FIG. 17B, the spatial frequency Fp when thevalue of the centroid spectrum Spcc is the greatest may be set as thereference spatial frequency Fb. Even in this case, the relationship(P_(H)>P_(L)) described above is satisfied.

Incidentally, the first evaluation value EV1 characterizing the balanceof the intensity of the centroid spectrum Spcc is calculated by thefollowing Expression (1) using the average intensities P_(H) and P_(L).

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack & \; \\{{{EV}\; 1} = \frac{1}{1 + ^{c{({P_{H} - P_{L}})}}}} & (1)\end{matrix}$

Here, c is a positive constant corresponding to the slope of the curveat P_(H)=P_(L). The right side of Expression (1) is so-called sigmoidfunction, and the first evaluation value EV1 is always a value equal toor greater than 0. When the value of the average intensity P_(H) issufficiently large, the first evaluation value EV1 approaches 0. On theother hand, when the value of the average intensity P_(H) issufficiently small, the first evaluation value EV1 approaches 1. Thatis, as the first evaluation value EV1 approaches 0, the centroidspectrum Spcc represents the characteristics of the “blue noise”.

[Second Evaluation Value V2]

FIGS. 18A and 18B are explanatory diagrams schematically showing amethod of calculating the root mean square (RMS) deviation of therespective centroid positions, which are disposed along a predetermineddirection, with respect to a direction perpendicular to thepredetermined direction.

As shown in FIG. 18A, first, a centroid position Pc1 as an initialposition is arbitrarily selected from the centroid position distributionC. Then, a centroid position Pc2, which is closest to the centroidposition Pc1, is selected. Then, a centroid position Pc3, which isclosest to the centroid position Pc2, is selected from the remainingcentroid position distribution C excluding the centroid position Pc1already selected. Subsequently, “N” centroid positions which aresufficient statistically (in the example shown in this diagram, for theconvenience of explanation, centroid positions Pc1 to Pc9 of ninepoints) are similarly selected. Then, the regression line of thecentroid positions Pc1 to Pc9 is calculated, and this straight line isdefined as a reference axis 430. This regression line may be determinedby using known analysis methods including the least squares method.

As shown in FIG. 18B, the reference axis 430 (in this diagram, writtenas an X′ axis) and a crossing axis 432 (in this diagram, written as a Y′axis), which is perpendicular to the reference axis 430, are set. Then,the RMS of each of the centroid positions Pc1 to Pc9, which are disposedalong the X′-axis direction (predetermined direction), with respect tothe Y′-axis direction (orthogonal direction) is calculated.

Subsequently, the centroid position Pc1 (initial position) is randomlyselected from the centroid position distribution C, and a trial tocalculate the RMS is repeated M times. Hereinafter, the value of the RMSobtained in an m-th (m=1, 2, . . . , M) trial is written as RMS(m).RMS(m) is calculated by the following Expression (2).

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack & \; \\{{{RMS}(m)} = \sqrt{\frac{\sum\limits_{k = 1}^{N}Y_{mk}^{2}}{N - 1}}} & (2)\end{matrix}$

Here, Y′mk corresponds to the Y′ coordinate of the k-th centroidposition Pck in the X′Y′ coordinate system in the m-th trial. As isunderstood from Expression (2). RMS(m) is always a value of 0 or more,and it can be said that the noise characteristic is improved as theRMS(m) approaches 0.

The second evaluation value EV2 is calculated by Expression (3) usingthe RMS(m) obtained in each trial and the average value RMSave thereof.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack & \; \\{{{EV}\; 2} = \sqrt{\frac{\sum\limits_{m = 1}^{M}\left( {{{RMS}(m)} - {RMS}_{ave}} \right)^{2}}{M - 1}}} & (3)\end{matrix}$

As is understood from Expression (3), the second evaluation value EV2 isalways a value of 0 or more, and it can be said that the regularity ofthe centroid position distribution C is high as the second evaluationvalue EV2 approaches 0. When the centroid position distribution C isregular (for example, periodical), the value of the RMS is approximatelyfixed regardless of the selection result of the initial position Pc1. Asa result, a variation in RMS(m) of each trial is reduced, and the valueof the second evaluation value EV2 is reduced. In this case, since theregularity of the centroid position distribution C is high,synchronization (interference) between the arrangement position of eachopening 18 and the arrangement position of each pixel 32 (the redsubpixel 32 r, the green subpixel 32 g, and the blue subpixel 32 b)occurs, and this tends to become noticeable as a color noise.

On the other hand, as shown in the example of FIG. 18A, in the case ofthe centroid position distribution C that is appropriately dispersed,the value of the RMS changes depending on the selection result of theinitial position Pc1. As a result, the value of the RMS(m) in each trialvaries, and the value of the second evaluation value EV2 is increased.In this case, since the regularity of the centroid position distributionC is low, synchronization (interference) between the arrangementposition of each opening 18 and the arrangement position of each pixel32 (the red subpixel 32 r, the green subpixel 32 g, and the bluesubpixel 32 b) does not occur. Accordingly, color noise is suppressed.

The second evaluation value EV2 may be equal to or greater than 15 μm,for example, in a range of 15 μm or more and 65 μm or less. It ispreferable that the second evaluation value EV2 be in a range of 26 μmor more and 65 μm or less, and a range of 26 μm or more and 36 μm orless is more preferable.

Incidentally, as shown in the examples of FIGS. 1A and 2A, in the caseof the mesh pattern 20 filled with polygonal shapes, the shape of eachopening 18 (or each mesh shape 22) is uniquely determined. Therefore, itis easy to calculate the opening area and the first and secondevaluation values EV1 and EV2. However, the opening area of the opening18 may not be uniquely determined due to the deformation and the like ofthe mesh shape 22. Therefore, in the claims and description of thepresent application, in order to clarify the definition of the first andsecond evaluation values EV1 and EV2, the opening area is defined asfollows.

FIGS. 19A to 19D are schematic explanatory diagrams of examples (firstto third examples) in which other elements are added in a region of theopening 18 a that is topologically closed. In these examples, elements(line elements) that form each closed region are extracted in advance,and the opening area of the opening 18 excluding elements other than theextracted line elements is calculated.

As shown in FIG. 19A, the opening area of the opening 18 a that istopologically closed is calculated as the area of a hatched region.Since the opening 18 a has a geometrically perfect quadrangular shape,the opening area can be uniquely calculated.

As shown in FIG. 198 as a first example, an opening 18 b in which apoint element 400 is formed in a portion (for example, a centralportion) of the opening 18 a shown in FIG. 19A is considered. In thiscase, the opening area of the opening 18 b is calculated as the area ofa region excluding the point element 400. That is, the opening 18 b istreated equivalently with the opening 18 a (refer to FIG. 19A).

As shown in FIG. 19C as a second example, an opening 18 c in which acircular line element 402 is formed in a portion of the opening 18 ashown in FIG. 19A is considered. In this case, the opening area of theopening 18 c is calculated as the area of a region excluding the lineelement 402. That is, the opening 18 c is treated equivalently with theopening 18 a (refer to FIG. 19A).

As shown in FIG. 19D as a third example, an opening 18 d having a lineelement 404 (so-called beard) that crosses the boundary line (in theexample shown in this diagram, one side of the quadrangle) of theopening 18 a shown in FIG. 19A and protrudes toward the inside of theopening 18 a is considered. In this case, the opening area of theopening 18 d is calculated as the area of a region excluding the lineelement 404. That is, the opening 18 d is treated equivalently with theopening 18 a (refer to FIG. 19A).

FIGS. 20A to 20D are schematic explanatory diagrams of examples (fourthto sixth examples) in which the mesh shape 22 is not formed since it istopologically open. In these examples, a closed region (hereinafter,referred to as a temporary region) is determined by supplementing theshortest virtual line for each line surrounding the opening 18, and thearea of the temporary region is calculated as the opening area of theopening 18.

However, it is defined that the opening area can be calculated only whenthe sum of the length of the supplemented virtual line is equal to orless than 20% of the total length of the boundary line that determinesthe temporary region. This is because each opening 18 cannot bespecified any longer if the sum of the length of the supplementedvirtual line exceeds 20% of the total length of the boundary line thatdetermines the temporary region.

As shown in FIG. 20A as a fourth example, the line surrounding anopening 18 e has a shape in which a part of the boundary line of theopening 18 a (refer to FIG. 19A) is missing. In this case, as shown inFIG. 20B, a temporary region 412 having the same shape as the opening 18a (refer to FIG. 19A) is determined by supplementing the shortest path(that is, a straight virtual line 410) between first and second endpoints 406 and 408. Therefore, the opening area of the opening 18 e iscalculated as the area of the temporary region 412. That is, the opening18 e is treated equivalently with the opening 18 a (refer to FIG. 19A).

As shown in FIG. 20C as a fifth example, the line surrounding an opening18 f has an arc shape in which a part of the circumference is missing.In this case, a temporary region 420 is determined by supplementing theshortest path (that is, a straight virtual line 418) between first andsecond end points 414 and 416. Therefore, the opening area of theopening 18 f is calculated as the area of the temporary region 420.

As shown in FIG. 20D as a sixth example, an opening 18 g is assumed tobe an open region interposed between a pair of parallel lines. In thiscase, a temporary region 426 having a rectangular shape is determined bysupplementing virtual lines 422 and 424 connecting the end points of theparallel lines. However, since the sum of the lengths of thesupplemented virtual lines 422 and 424 exceeds 20% of the total lengthof the boundary line that determines the temporary region 426, it is notpossible to calculate the opening area. Accordingly, this is excludedfrom the calculation of the first and second evaluation values EV1 andEV2.

Thus, the noise characteristics of the conductive sheets 10 and 11 canbe quantified in various ways using the first evaluation value EV1(refer to Expression (1)) and the second evaluation value EV2 (refer toExpressions (2) and (3)).

Subsequently, the effects obtained when setting the relative refractiveindex nr1 of the transparent base 12 with respect to the firstprotective layer 26 a to a value close to 1 will be described in detailwith reference to FIGS. 21A to 22B. For easy understanding, a part ofthe configuration of the conductive sheet 11 is omitted, and only thetransparent base 12, the first conductive portion 14 a, and the firstprotective layer 26 a are shown.

As shown in FIG. 21A, parallel light 102 emitted from the display unit30 side (refer to FIG. 4) enters inside of the transparent base 12 andmoves straight along the arrow Z1 direction. Then, almost all of theparallel light 102 is reflected in the arrow Z2 direction, as reflectedcomponent 106, on a first interface 104 between the transparent base 12and the thin metal wire 16. That is, depending on the presence orabsence of the thin metal wire 16 formed of a non-translucent material,a difference in the amount of light transmitted through the conductivesheet 11 becomes large. As a result, shading according to the shape ofthe mesh pattern 20 becomes noticeable, and thus moire is easilygenerated. In contrast, in the case of a conductive sheet using aconductive material (typically, ITO) having high translucency, there islittle influence described above.

Hereinafter, an optical phenomenon when the refractive index differencebetween the transparent base 12 and the first protective layer 26 a islarge, that is, an optical phenomenon when the relative refractive indexnr1 is away from 1 will be described with reference to FIGS. 21B and21C.

As shown in FIG. 21B, light that is slightly inclined with respect tothe arrow Z1 direction (obliquely incident light 108) enters inside ofthe transparent base 12, and moves straight to a second interface 110between the first conductive portion 14 a (opening 18) and the firstprotective layer 26 a. Then, a part of the obliquely incident light 108is transmitted (to be straight component 112), and the remaining lightis reflected (to be reflected component 114) due to the refractionphenomenon on the second interface 110. At this time, since the relativerefractive index nr1 is away from 1, the interface transmittance isreduced, and the amount of light of the straight component 112 (or thereflected component 114) is relatively decreased (or increased).

For example, as shown in FIG. 21C, it is assumed that the amount oflight of I=Iw at a position corresponding to the opening 18 and theamount of light of I=Ib at a position corresponding to the thin metalwire 16 are detected after the light is transmitted through theconductive sheet 11. In this case, the optical intensity due to the thinmetal wire 16 is expressed as ΔD1=−log(Ib/Iw) with the detected amountof light in the opening 18 as a reference.

Next, an optical phenomenon when the refractive index difference betweenthe transparent base 12 and the first protective layer 26 a is small,that is, an optical phenomenon when the relative refractive index nr1 isa value close to I will be described with reference to FIGS. 22A and22B.

When the relative refractive index nr1 is a value close to 1, theinterface transmittance approaches 1 (the interface reflectanceapproaches 0) as is easily derived from the optical considerations.Therefore, the amount of light of straight component 116 (or reflectedcomponent 118) is relatively increased (or decreased) compared with thatin the case shown in FIG. 21B. In other words, the amount of lightpassing through the inside of the transparent base 12 without beingscattered is uniformly increased regardless of the position of the thinmetal wire 16 formed of a non-translucent material. Hereinafter, for theconvenience of explanation, it is assumed that the detected amount oflight has increased by ε (positive value).

At this time, as shown in FIGS. 22A and 22B, the amount of light ofI=Iw+ε and the amount of light of I=Ib+ε are detected at a positioncorresponding to the opening 18 and at a position corresponding to thethin metal wire 16, respectively, after the transmission of the light.The optical intensity due to the thin metal wire 16 is expressed asΔD2=−log {(Ib+ε)/(Iw+ε)} with the detected amount of light in theopening 18 as a reference.

When Iw>Ib≧0 and ε>0, the inequality of (Ib/Iw)<(Ib+ε)/(Iw+ε) issatisfied. Accordingly, the relationship of ΔD1>ΔD2 is always satisfied.That is, the contrast of the optical intensity due to the thin metalwire 16 can be reduced by setting the relative refractive index nr1 ofthe transparent base 12 and the first protective layer 26 a to a valueclose to 1. As a result, in plan view of the display device 40, thedesign of the thin metal wire 16 is less likely to be visible to theuser.

The above is true for the relationship between the transparent base 12and the second protective layer 26 b as well as the relationship betweenthe transparent base 12 and the first protective layer 26 a. It ispreferable that the relative refractive indices nr1 and nr2 be 0.86 to1.15, and 0.91 to 1.08 is more preferable. In particular, it is furtherpreferable that the first protective layer 26 a and/or the secondprotective layer 26 b be formed of the same material as the transparentbase 12 since nr1=1 (nr2=1) is satisfied.

As described above, since the relative refractive index nr1 of thetransparent base 12 with respect to the first protective layer 26 aand/or the relative refractive index nr2 of the transparent base 12 withrespect to the second protective layer 26 b are set to 0.86 to 1.15, theamount of light (straight components 116) that moves straight on theinterface between the transparent base 12 and the first protective layer26 a and/or the interface between the transparent base 12 and the secondprotective layer 26 b, of light (obliquely incident light 108) that isincident slightly obliquely with respect to the normal direction (arrowZ1 direction) of the transparent base 12, is relatively increased. Thatis, the amount of light passing through the transparent base 12 withoutbeing scattered is uniformly increased regardless of the position of thethin metal wire 16 formed of a non-translucent material. Accordingly,since the contrast of the optical intensity due to the thin metal wire16 can be reduced, the design of the thin metal wire 16 is less likelyto be visible to the viewer (user). In particular, in the mesh pattern20 in which different mesh shapes 22 are arrayed without space, it ispossible to suppress the occurrence of the granular feeling of noise.Accordingly, the above configuration is more effective for the meshpattern 20 in which different mesh shapes 22 are arrayed without space.It is needless to say that the effects described above be obtained notonly when each mesh shape 22 is a polygonal shape but also when eachmesh shape 22 has various shapes.

Next, the effects obtained by providing the first dummy pattern 76 a inthe conductive sheet 11 will be described with reference to FIGS. 23A to24C. For easy understanding, the configuration of the first protectivelayer 26 a and the like is omitted, and an optical phenomenon will bedescribed on the assumption that the influence due to the lightrefraction effect is little.

FIG. 23A is a schematic plan view of a first sensor portion 120according to a reference example. The first sensor portion 120 isconfigured to include only the first conductive patterns 70 a, and has aform in which there is no first dummy pattern 76 a (refer to FIGS. 5Aand 6).

FIG. 23B is a schematic explanatory diagram showing the path of externallight 122 incident on the first sensor portion 120. This diagram isequivalent to the schematic cross-sectional view of the first conductivepattern 70 a near the boundary Bd shown in FIG. 23A.

The position P1 is equivalent to a position where no thin metal wire 16is present in both the first and second conductive portions 14 a and 14b. The external light 122 emitted from the outside of the display device40 (refer to FIG. 4) enters inside of the conductive sheet 11 and movesstraight approximately in parallel along the arrow Z2 direction. Then,almost all of the external light 122 is transmitted in the arrow Z2direction on the first interface 104 between the opening 18 and thetransparent base 12. At this time, a part of the transmitted light movesstraight along the arrow Z2 direction as straight component 124, and apart of the remaining light is scattered as scattering component 126.Then, almost all of the straight component 124 is transmitted in thearrow Z2 direction on a third interface 128 between the transparent base12 and the opening 18. A part of the transmitted light moves straightalong the arrow Z2 direction as straight component 130, and a part ofthe remaining light is scattered as scattering component 132. As aresult, most of the external light 122 emitted to the position P1 isreleased in the arrow Z2 direction of the conductive sheet 11.

The position P2 is equivalent to a position where the thin metal wire 16is present in the first conductive portion 14 a and the thin metal wire16 is not present in the second conductive portion 14 b. Most of theexternal light 122 emitted from the outside of the display device 40(refer to FIG. 4) is reflected in the arrow Z1 direction, as reflectedcomponent 134, on the surface of the first conductive portion 14 a (thinmetal wire 16 formed of a non-translucent material).

The position P3 is equivalent to a position where the thin metal wire 16is not present in the first conductive portion 14 a and the thin metalwire 16 is present in the second conductive portion 14 b. The externallight 122 emitted from the outside of the display device 40 (refer toFIG. 4) enters inside of the conductive sheet 11 and moves straightapproximately in parallel along the arrow Z2 direction. Then, almost allof the external light 122 is transmitted in the arrow Z2 direction onthe first interface 104. At this time, a part of the transmitted lightmoves straight along the arrow Z2 direction as the straight component124, and a part of the remaining light is scattered as the scatteringcomponent 126. Then, almost all of the straight component 124 isreflected in the arrow Z1 direction, as reflected component 135, on thethird interface 128 (surface of the thin metal wire 16 formed of anon-translucent material). Then, the reflected component 135 movesstraight through the transparent base 12 along the arrow Z1 direction,and almost all of the reflected component 135 is transmitted in thearrow Z1 direction on the first interface 104. As a result, a part ofthe external light 122 emitted to the position P3 is released to theoutside (arrow Z1 direction side) of the conductive sheet 11 as straightcomponent 136 (or scattering component 137).

As described above, it is understood that the amount of reflected lightIr (reflected light 134) at the position P2 is larger than the amount ofreflected light Ir (straight component 136) at the position P3. This isdue to a difference in optical path lengths to reach the position of thethin metal wire 16 (equivalent to twice the thickness of the transparentbase 12).

FIG. 23C is a graph showing the intensity distribution of reflectedlight in the first sensor portion 120 shown in FIG. 23A. The horizontalaxis of the graph indicates the position in the arrow X direction, andthe vertical axis of the graph indicates the intensity of reflectedlight (the amount of reflected light Ir). The amount of reflected lightIr means the amount of light reflected toward the one surface side(arrow Z1 direction side) of the conductive sheet 11 when the uniformexternal light 122 enters regardless of the position in the arrow Xdirection.

As a result, at a position where the first conductive pattern 70 a isnot present in the first sensor portion 120, the amount of reflectedlight Ir is a minimum value (Ir=I1). At a position where the firstconductive pattern 70 a is present in the first sensor portion 120, theamount of reflected light Ir is a maximum value (Ir=I2). That is, theamount of reflected light Ir has a characteristic according to theregular arrangement of the first sensing portion 72 a, in other words, aperiodic characteristic in which the minimum value (I1) and the maximumvalue (I2) are alternately repeated.

In contrast, in the case of a conductive sheet using a conductivematerial (typically, ITO) having high translucency, the amount ofreflected light Ir is equal to approximately 0 (I1=I2=0). For thisreason, there is almost no contrast (brightness difference) due to thepresence or absence of the first conductive pattern 70 a. That is,compared with the case where the thin metal wire 16 is applied to thefirst conductive pattern 70 a, there is almost no influence describedabove.

Meanwhile, FIG. 24A is a schematic plan view of the first sensor portion60 a (refer to FIGS. 5A and 6) according to the present embodiment. Thefirst sensor portion 60 a is configured to include the first conductivepattern 70 a and the first dummy pattern 76 a.

FIG. 24B is a schematic explanatory diagram showing the path of theexternal light 122 incident on the first sensor portion 60 a. Thisdiagram is equivalent to the schematic cross-sectional view of the firstconductive pattern 70 a near the boundary Bd shown in FIG. 24A.

Explanation regarding a position Q1 corresponding to the position P1will be omitted since it is the same as that shown in FIG. 23B. This isthe same for a position Q2 corresponding to the position P2.

At a position Q3 corresponding to the position P3, most of the externallight 122 emitted from the outside of the display device 40 (refer toFIG. 4) is reflected in the arrow Z1 direction, as reflected component138, on the surface of the first dummy electrode portion 15 a (thinmetal wire 16 formed of a non-translucent material). That is, theconductive sheet 11 reflects the external light 122 to the same extentas the position Q2 regardless of the presence or absence of the thinmetal wire 16 in the second conductive portion 14 b.

As a result, as shown in FIG. 24C, the amount of reflected light Ir hasa uniform characteristic of Ir=I2 regardless of the regular arrangementof the first sensing portion 72 a. In a spacing portion of the firstconductive portion 14 a and the first dummy electrode portion 15 a, atendency that the amount of reflected light Ir is reduced slightly (byan amount of E) is observed. By reducing the width of the spacingportion, the shape of the first sensing portion 72 a is much less likelyto be visible.

As described above, since the wiring density of the first dummy pattern76 a disposed in the first opening portion 75 a between the adjacentfirst conductive patterns 70 a is equal to the wiring density of thefirst conductive pattern 70 a, the light reflectance in a planar regionof the first dummy pattern 76 a for the external light 122 from one mainsurface side is approximately the same as the light reflectance in aplanar region of the first conductive pattern 70 a. That is, it ispossible to make the intensity distribution of reflected light(reflected components 134 and 138) uniform regardless of the regulararrangement of the first sensing portion 72 a. Accordingly, even in aconfiguration in which an electrode formed of the thin metal wire 16 isformed on both surfaces of the transparent base 12, it is possible tosuppress the visibility of the first sensing portion 72 a (or the secondsensor 72 b) due to the external light 122 as a light source of thereflected light.

FIG. 25 is a block diagram showing the schematic configuration of amanufacturing apparatus 310 for producing the conductive sheets 10 and11 according to the present embodiment.

The manufacturing apparatus 310 basically includes: an image generationapparatus 312 that generates the image data Img (including output imagedata ImgOut) representing a design (wiring shape) corresponding to themesh pattern 20; a first light source 148 a that irradiates one mainsurface of a conductive sheet (photosensitive material 140; refer toFIG. 36A) with first light 144 a to expose the conductive sheet in themanufacturing process in order to implement the design represented bythe output image data ImgOut generated by the image generation apparatus312; a second light source 148 b that irradiates the other main surfaceof the photosensitive material 140 with second light 144 b to expose thephotosensitive material 140 on the basis of the output image dataImgOut; an input unit 320 that inputs various conditions for generatingthe image data Img (including the viewing information of the meshpattern 20 or the black matrix 34) to the image generation apparatus312; and a display unit 322 that displays a GUI image to assist theinput work using the input unit 320, the stored output image dataImgOut, and the like.

The image generation apparatus 312 includes: a storage unit 324 thatstores the image data Img, the output image data ImgOut, position dataSPd of a candidate point SP, and position data SDd of a seed point SD; arandom number generation unit 326 that generates a random number bygenerating a pseudo-random number; an initial position selection unit328 that selects the initial position of the seed point SD from apredetermined two-dimensional image region using the random numbergenerated by the random number generation unit 326; an update candidateposition determination unit 330 that determines the position of thecandidate point SP (excluding the position of the seed point SD) fromthe two-dimensional image region using the random number describedabove; an image cutting unit 332 that cuts out first image data andsecond image data (to be described later) from the output image dataImgOut; and a display control unit 334 that performs control to displayvarious images on the display unit 322.

The seed point SD includes a first seed point SDN that is not to beupdated and a second seed point SDS that is to be updated. In otherwords, the position data SDd of the seed point SD includes position dataSDNd of the first seed point SDN and position data SDSd of the secondseed point SDS.

In addition, a control unit (not shown) which includes a CPU and thelike can realize various controls regarding image processing by readingand executing a program recorded on the recording medium (ROM (notshown) or the storage unit 324).

The image generation apparatus 312 further includes: an imageinformation estimation unit 336 that estimates image informationcorresponding to the mesh pattern 20 on the basis of viewing information(to be described in detail later) input through the input unit 320; animage data generation unit 338 that generates the image data Img, whichrepresents a design corresponding to the mesh pattern 20, on the basisof the image information supplied from the image information estimationunit 336 and the position of the seed point SD supplied from the storageunit 324; a mesh design evaluation unit 340 (evaluation valuecalculation unit) that calculates an evaluation value EVP for evaluatingthe design of the mesh shape 22 on the basis of the image data Imggenerated by the image data generation unit 338; and a data updateinstruction unit 342 (image data determination unit) that gives aninstruction regarding the update/non-update of data, such as the seedpoint SD and the evaluation value EVP, or regarding the determination ofthe output image data ImgOut, on the basis of the evaluation value EVPcalculated by the mesh design evaluation unit 340.

Hereinafter, a method of generating image data, which is supplied toform the output of the mesh pattern 20, will be described while mainlyreferring to the flowchart of FIG. 26 and the configuration blockdiagram of FIG. 25.

In step S1, the input unit 320 inputs various kinds of informationrequired for the determination of the wiring shape of the mesh pattern20. The operator inputs viewing information regarding the visibility ofthe mesh pattern 20 through the display unit 322. The viewinginformation of the mesh pattern 20 is various kinds of informationcontributing to the shape or the optical intensity of the mesh pattern20. For example, the viewing information of the mesh pattern 20 mayinclude at least one of the material, color value, light transmittance,light reflectance, cross-sectional shape, and thickness of the thinmetal wire 16. In addition, at least one of the material, color value,light transmittance, light reflectance, and film thickness of thetransparent base 12 may be included.

Then, the image information estimation unit 336 estimates imageinformation corresponding to the mesh pattern 20 on the basis of thevarious kinds of information input through the input unit 320. Forexample, the number of pixels in the vertical direction of output imagedata ImgOut can be calculated on the basis of the vertical size of themesh pattern 20 and the image resolution of the output image dataImgOut. In addition, the number of pixels corresponding to the linewidth of the thin metal wire 16 can be calculated on the basis of thewidth of the wiring line and the image resolution described above.Further, it is possible to estimate the number of openings 18 and thenumber of seed points SD on the basis of the light transmittance of thethin metal wire 16, the light transmittance of the transparent base 12,a total transmittance required, and the width of the wiring line.

Then, the output image data ImgOut is generated (step S2). Prior toexplaining the method of generating the output image data ImgOut, amethod of evaluating the image data Img will be described first. In thepresent embodiment, evaluation is performed on the basis of theevaluation value EVP quantifying the noise characteristics (for example,granular noise).

The reference evaluation value EV0 is calculated by the followingExpression (4) assuming that the value of the spectrum Spc is F(Ux, Uy).

[Equation 4]

EV0={∫_(−Umax) ^(Umax)∫_(−Umax) ^(Umax) VTF(√{square root over (Ux ² +Uy²)})F(Ux,Uy)dUxdUy} ^(1/2)  (4)

According to the theorem of Wiener-Khintchine, a value obtained byintegrating the spectrum Spc in the entire spatial frequency bandcorresponds to the square of the RMS. A value obtained by multiplyingthe spectrum Spc by VTF and integrating the new spectrum Spc in theentire spatial frequency band is an evaluation index that approximatelymatches the visual characteristics of human. The reference evaluationvalue EV0 can be referred to as RMS after correction using the visualresponse characteristics of human. Similarly to the normal RMS, thereference evaluation value EV0 is always a value of 0 or more, and itcan be said that the noise characteristic is improved as the valueapproaches 0.

The actual visual response characteristics of human have a value smallerthan 1 in the vicinity of 0 cycle/mm, and thus have so-called band passfilter characteristics. In the present embodiment, however, asillustrated in FIG. 11, contribution to the reference evaluation valueEV0 is increased by setting the value of the VTF to 1 even in a very lowspatial frequency band. Thus, the effect of suppressing the periodicitydue to the repeated arrangement of the mesh patterns 20 is obtained.

Other than the above reference evaluation value EV0, the evaluationvalue EVP can be calculated by the following Expression (5) using thefirst and second evaluation values EV1 and EV2 described above.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack & \; \\{{EVP} = {\sum\limits_{j = 0}^{2}{\alpha \; {j \cdot {EVj}}}}} & (5)\end{matrix}$

Here, αj (j=0 to 2) is a coefficient that determines the specificgravity of the respective evaluations. It is needless to say that notonly the value of the coefficient αj but also the calculation expressionof the evaluation value EVP can be modified in various ways according tothe target level (allowable range) or the evaluation function fordetermining the mesh pattern 20.

For example, the degree of variation for the spectrum Spc in the angulardirection (first evaluation value EV1) or for the centroid positionalong a predetermined direction (second evaluation value EV2) may bequantified using various statistical values. Here, the “statisticalvalues” are calculated values that are calculated using a statisticalmethod. For example, the “statistical values” may be not only a mean anda standard (RMS) deviation but also a mode, a central value, a maximumvalue, and a minimum value. In addition, it is also possible to performstatistical processing, such as a histogram, and then quantify thedegree of variation from the shape and the like.

Hereinafter, a specific method of determining the output image dataImgOut on the basis of the aforementioned evaluation value EVP will bedescribed. For example, it is possible to use a method of sequentiallyrepeating the generation of a dot pattern including a plurality of seedpoints SD, the generation of the image data Img based on the pluralityof seed points SD, and the evaluation based on the evaluation value EVP.Here, various optimization methods can be used as the algorithm ofdetermining the positions of the plurality of seed points SD. Forexample, as an optimization technique to determine the dot pattern, itis possible to use various search algorithms, such as a constructivealgorithm or a sequential improvement algorithm. A neural network, agenetic algorithm, a simulated annealing method, and a void-and-clustermethod can be mentioned as specific examples.

In the present embodiment, a method of optimizing the design of the meshpattern 20 based on the simulated annealing method (hereinafter,referred to as an SA method) will be described while mainly referring tothe flowchart of FIG. 27 and the functional block diagram of FIG. 25.The SA method is a stochastic search algorithm that imitates the“annealing method” for obtaining the robust iron by striking the iron ina high temperature state.

In step S21, the initial position selection unit 328 selects the initialposition of each seed point SD. Prior to the selection of the initialposition, the random number generation unit 326 generates a randomnumber using a pseudo-random number generation algorithm. Then, theinitial position selection unit 328 determines the initial position ofeach seed point SD randomly using the random number supplied from therandom number generation unit 326. Here, the initial position selectionunit 328 selects the initial position of each seed point SD as anaddress of the pixel on the image data Img, and sets it as a positionwhere the seed points SD do not overlap each other.

In step S22, the image data generation unit 338 generates image dataImgInit as initial data. The image data generation unit 338 generatesthe image data ImgInit (initial data) representing a designcorresponding to the mesh pattern 20 on the basis of the position dataSDd or the number of seed points SD supplied from the storage unit 324and the image information supplied from the image information estimationunit 336.

Prior to the generation of the image data Img (including the image dataImgInit), definitions of the pixel address and the pixel value aredetermined in advance.

FIG. 28A is an explanatory diagram showing the definition of the pixeladdress in the image data Img. For example, it is assumed that the pixelsize is 10 μm and the number of pixels in the image data is 8192 each inthe horizontal and vertical direction. For convenience of explanation ofthe FFT calculation process to be described later, the number ofhorizontal and vertical pixels in the image data is set to be the powerof 2 (for example, 13 power of 2). In this case, the entire image regionof the image data Img is equivalent to a rectangular region of about82-mm square.

FIG. 28B is an explanatory diagram showing the definition of the pixelvalue in the image data Img. For example, the number of gray-scalelevels per pixel is set to 8 bits (256 gray-scale levels). The opticalintensity 0 is made to correspond to the pixel value 0 (minimum value),and the optical intensity 4.5 is made to correspond to the pixel value255 (maximum value). In the pixel values 1 to 254 therebetween, valuesare determined so as to have a linear relationship with the opticalintensity. The definition of the pixel value may be color values, suchas tristimulus values XYZ or RGB and L*a*b*, as well as the opticalintensity.

In this manner, the image data generation unit 338 generates the imagedata ImgInit corresponding to the mesh pattern 20 on the basis of thedata definition of the image data Img and the image informationestimated by the image information estimation unit 336 (step S22).

The image data generation unit 338 determines the initial state of themesh pattern 20 shown in FIG. 29B using various region determinationalgorithms (for example, a Voronoi diagram and a Delaunay diagram) withthe initial position (refer to FIG. 29A) of the seed point SD as areference.

Incidentally, when the size of the image data Img is very large, theamount of arithmetic processing for optimization becomes enormous. Inthis case, the processing capacity and the processing time of the imagegeneration apparatus 312 are required. In addition, since the size ofthe image data Img (output image data ImgOut) is large, the memorycapacity to store the image data Img is also required. Therefore, amethod of making the image data Img have a repeated shape by regularlyarranging unit image data ImgE satisfying predetermined boundaryconditions is effective. Hereinafter, the specific method will bedescribed in detail with reference to FIGS. 30 and 31.

FIG. 30 is a schematic explanatory diagram showing a method ofdetermining a design at the end of a unit region 90. FIG. 31 is aschematic explanatory diagram showing the result when the unit imagedata ImgE is regularly arrayed to generate the image data Img.

As shown in FIG. 30, in the unit region 90 having an approximatelysquare shape, points P₁₁ to P₁₄ are disposed in the upper right corner,upper left corner, lower left corner, and lower right corner,respectively. For the convenience of explanation, only four points ofthe points P₁₁ to P₁₄ present in the unit region 90 are expressed, andother points are omitted.

A virtual region 92 (indicated by a dotted line) having the same size asthe unit region 90 is disposed adjacent to the right side of the unitregion 90. On the virtual region 92, a virtual point P₂₂ is disposed soas to correspond to the position of the point P₁₂ in the unit region 90.In addition, a virtual region 94 (indicated by a dotted line) having thesame size as the unit region 90 is disposed adjacent to the upper rightside of the unit region 90. On the virtual region 94, a virtual pointP₂₃ is disposed so as to correspond to the position of the point P₁₃ inthe unit region 90. Further, a virtual region 96 (indicated by a dottedline) having the same size as the unit region 90 is disposed adjacent tothe upper side of the unit region 90. On the virtual region 96, avirtual point P₂₄ is disposed so as to correspond to the position of thepoint P₁₄ in the unit region 90.

Then, under this condition, the image data generation unit 338determines a design (wiring shape) in the upper right corner of the unitregion 90 according to the Voronoi diagram (splitting method).

In the relationship between the point P₁₁ and the virtual point P₂₂, adivision line 97, which is a set of points whose distances from thepoint P₁₁ and the virtual point P₂₂ are equal, is determined. Inaddition, in the relationship between the point P₁₁ and the virtualpoint P₂₄, a division line 98, which is a set of points whose distancesfrom the point P₁₁ and the virtual point P₂₄ are equal, is determined.Further, in the relationship between the virtual point P₂₂ and thevirtual point P₂₄, a division line 99, which is a set of points whosedistances from the virtual points P₂₂ and P₂₄ are equal, is determined.By these division lines 97 to 99, a pattern in the upper right corner ofthe unit region 90 is determined. Similarly, patterns at all ends of theunit region 90 are determined. Hereinafter, image data in the unitregion 90 generated in this manner is referred to as the image dataImgE.

As shown in FIG. 31, the image data Img is generated in the planarregion 100 by arraying the unit image data ImgE regularly facing in thesame direction and in the horizontal and vertical directions. Since thedesign is determined according to the boundary conditions shown in FIG.30, seamless connection can be made between the upper and lower ends ofthe unit image data ImgE and between the right and left ends of the unitimage data ImgE.

By this configuration, it is possible to reduce the size of the unitimage data ImgE. As a result, it is possible to reduce the amount ofarithmetic processing and the data size. In addition, moire due to themismatch of the seam is not generated. The shape of the unit region 90is not limited to the square shown in FIGS. 30 and 31, and any shapethat can be arrayed without space, such as a rectangle, a triangle, anda hexagon, can be used.

In step S23, the mesh design evaluation unit 340 calculates anevaluation value EVPInit as an initial value. In the SA method, theevaluation value EVP serves as a cost function. The mesh patternevaluation unit 340 acquires the spectrum Spc by performing a fastFourier transformation (FFT) on the image data ImgInit, and thencalculates the evaluation value EVP on the basis of the spectrum Spc. Itis needless to say that the calculation expression of the evaluationvalue EVP can be modified in various ways according to the target level(allowable range) or the evaluation function for determining the meshpattern 20.

In step S24, the storage unit 324 temporarily stores the image dataImgInit generated in step S22 as Img and the evaluation value EVPInitcalculated in step S23 as EVP. At the same time, an initial value nΔT (nis a natural number, and ΔT is a positive real number) is substitutedfor the pseudo-temperature T.

In step S25, the mesh design evaluation unit 340 initializes a variableK. That is, 0 is substituted for K.

Then, in a state where some of the seed points SD (second seed pointSDS) are replaced with candidate points SP, image data ImgTemp isgenerated and evaluation value EVPTemp is calculated, and then “update”or “non-update” of the seed point SD is determined (step S26). This stepS26 will be described in more detail with reference to the flowchart ofFIG. 32 and the functional block diagram of FIG. 25.

In step S261, the update candidate position determination unit 330extracts and determines the candidate point SP from the predeterminedplanar region 100. The update candidate position determination unit 330determines a position, which does not overlap any position of the seedpoint SD in the image data Img, for example, using the random numbersupplied from the random number generation unit 326. The number ofcandidate points SP may be 1 or more. In an example shown in FIG. 33A,the number of current seed points SD is 8 (points P₁ to P₈), while thenumber of candidate points SP is 2 (points Q₁ and Q₂).

In step S262, some of the seed points SD are exchanged for the candidatepoints SP at random. The update candidate position determination unit330 correlates the seed point SD, which is exchanged for (or updated to)a candidate point SP, with the candidate point SP at random. In FIG.33A, it is assumed that the point P₁ is correlated with the point Q₁ andthe point P₃ is correlated with the point Q₂. As shown in FIG. 33B, thepoint P₁ is exchanged for the point Q₁, and the point P₃ is exchangedfor the point Q₂. Here, the points P₂ and P₄ to P₈ not to be exchanged(or not to be updated) are referred to as a first seed point SDN, andthe points P₁ and P₃ to be exchanged (or to be updated) are referred toas a second seed point SDS.

In step S263, the image data generation unit 338 generates the imagedata ImgTemp on the basis of the exchanged new seed point SD (refer toFIG. 33B) and the image information estimated by the image informationestimation unit 336 (refer to the explanation of step S1). In this case,since the same method as in step S22 (refer to FIG. 27) is used,explanation thereof will be omitted.

In step S264, the mesh design evaluation unit 340 calculates theevaluation value EVPTemp on the basis of the image data ImgTemp. In thiscase, since the same method as in step S23 (refer to FIG. 27) is used,explanation thereof will be omitted.

In step S265, the data update instruction unit 342 calculates an updateprobability Prob of the position of the seed point SD. Here, the “updateof the position” refers to determining the seed point SD obtained bytemporary exchange in step S262 (that is, the first seed point SDN andthe candidate point SP) as the new seed point SD.

Specifically, the probability of updating or non-updating the seed pointSD is calculated according to the metropolis criterion. The updateprobability Prob is given by the following Expression (6).

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack & \; \\{P_{rob} = \left\{ \begin{matrix}{1} & \left( {{{if}\mspace{14mu} {EVPTemp}} < {EVP}} \right) \\{{\exp \left( {- \frac{{EVPTemp} - {EVP}}{T}} \right)}} & \left( {{{if}\mspace{14mu} {EVPTemp}} \geq {EVP}} \right)\end{matrix} \right.} & (6)\end{matrix}$

Here, T indicates a pseudo-temperature, and the update rule of the seedpoint SD changes from “stochastic” to “deterministic” as the temperatureapproaches the absolute temperature (T=0).

In step S266, the data update instruction unit 342 determines whether ornot to update the position of the seed point SD according to thecalculated update probability Prob. For example, whether or not toupdate the position of the seed point SD may be stochasticallydetermined using the random number supplied from the random numbergeneration unit 326. The data update instruction unit 342 gives aninstruction of “update” to the storage unit 324 when the seed point SDis updated, and gives an instruction of “non-update” to the storage unit324 when the seed point SD is not updated (steps S267 and S268).

Thus, step S26 of determining whether to replace (update) some of theseed points SD (second seed point SDS) with the candidate points SP ornot (non-update) is completed.

Referring back to FIG. 27, according to the instruction of either“update” or “non-update” of the position of the seed point SD, whetheror not to update the seed point SD is determined (step S27). The processproceeds to the next step S28 when the seed point SD is updated, and theprocess skips step S28 and proceeds to step S29 when the seed point SDis not updated.

In step S28, when updating the seed point SD, the storage unit 324overwrites the image data Img, which is currently stored, to replace itwith the image data ImgTemp calculated in step S263. In addition, thestorage unit 324 overwrites the evaluation value EVP, which is currentlystored, to replace it with the evaluation value EVPTemp calculated instep S264. Further, the storage unit 324 overwrites the position dataSDSd of the second seed point SDS, which is currently stored, to replaceit with the position data SPd of the candidate point SP calculated instep S261. Then, the process proceeds to the next step S29.

In step S29, the data update instruction unit 342 adds 1 to the value ofK at the present time.

In step S30, the data update instruction unit 342 performs a sizecomparison between the value of K at the present time and the value ofKmax determined in advance. When the value of K is smaller than Kmax,the process returns to step S26 to repeat the steps S26 to S29. WhenK>Kmax is satisfied, the process proceeds to the next step S31.

In step S31, the data update instruction unit 342 subtracts ΔT from thepseudo-temperature T. The variation of the pseudo-temperature ΔT may bethe multiplication of the constant δ (0<δ<1) instead of the subtractionof ΔT. In this case, a predetermined value is subtracted from theprobability Prob (bottom) shown in Expression (6).

In step S32, the data update instruction unit 342 determines whether ornot the pseudo-temperature T at the present time is equal to 0. When Tis not equal to 0, the process returns to step S25 to repeat the stepsS25 to S31. On the other hand, when T is equal to 0, the data updateinstruction unit 342 notifies the storage unit 324 that the evaluationbased on the SA method has been completed.

In step S33, the storage unit 324 overwrites the contents of the imagedata Img, which has been updated last in step S28, to replace it withthe output image data ImgOut. Thus, the generation of the output imagedata ImgOut (step S2) is ended.

Since the image data Img representing the design of the mesh pattern 20obtained by arraying different mesh shapes 22 is generated, theevaluation value EVP is calculated by quantifying the degree ofvariation of the centroid position of each mesh shape 22 on the basis ofthe image data Img, and a piece of image data Img is determined as theoutput image data ImgOut on the basis of the evaluation value EVP andpredetermined evaluation conditions, it is possible to determine eachmesh shape 22 having noise characteristics which satisfy thepredetermined evaluation conditions. In other words, by controlling theshape of the mesh pattern 20 appropriately, it is possible to suppressthe generation of both the moire and the granular feeling of noise.

It is preferable to calculate the first evaluation value EV1 on thebasis of the centroid spectrum Spcc for the centroid positiondistribution C. Further, regarding the centroid position distribution C,it is preferable that the statistical value of the centroid position,which is disposed along the reference axis 430, with respect to thecrossing axis 432 be calculated as the second evaluation value EV2.

The output image data ImgOut may be image data representing wiringshapes of electrodes for various devices such as an inorganic EL device,an organic EL device, or a solar cell, as well as the touch panel 44. Inaddition to electrodes, applications can also be made to a transparentheating element that generates heat when a current is caused to flow(for example, a defroster of a vehicle) and an electromagnetic shieldingmaterial to block electromagnetic waves.

Referring back to FIG. 26, finally, the image cutting unit 332 cuts twoor more first conductive patterns 70 a, two or more first dummy patterns76 a, and two or more second conductive patterns 70 b from the shape ofthe planar region 100 (design of the mesh pattern 20) represented by theoutput image data ImgOut (step S3).

FIG. 34A is a schematic explanatory diagram showing a result of thecutting of the first conductive pattern 70 a and the first dummy pattern76 a. FIG. 34B is a schematic explanatory diagram showing a result ofthe cutting of the second conductive pattern 70 b.

By cutting a portion excluding a first region R1 (hatched region) fromthe planar region 100 shown in FIG. 34A, first image data representing adesign on one main surface side (arrow s1 direction side in FIG. 2B) ofthe transparent base 12 is generated. The first region R1 has a shape inwhich a plurality of rhombic frames are connected to each other in thearrow X direction. That is, the first image data represents two or morefirst conductive patterns 70 a and two or more first dummy patterns 76 a(refer to FIG. 6 and the like).

By cutting out only a second region R2 (hatched region) from the planarregion 100 shown in FIG. 34B, second image data representing a design onthe other main surface side (arrow s2 direction side in FIG. 2B) of thetransparent base 12 is generated. The second image data represents twoor more second conductive patterns 70 b (refer to FIG. 7 and the like).A region excluding the second region R2 (blank region in the planarregion 100 shown in FIG. 34B) corresponds to the position of each firstconductive pattern 70 a.

In FIGS. 34A and 34B, the planar region 100 is disposed in a state ofbeing inclined by a predetermined angle (for example, θ=45) comparedwith FIG. 31. That is, the angle θ formed by the arrangement directionof the unit image data ImgE and the extending direction of the firstconductive pattern 70 a (or the second conductive pattern 70 b) is not0° (0°<θ<90°). Thus, since the first conductive pattern 70 a (or thesecond conductive pattern 70 b) is inclined by the predetermined angle θwith respect to the arrangement direction of the repeated shape of themesh pattern 20, it is possible to suppress the generation of moirebetween the first sensing portion 72 a (or the second sensing portion 72b) and the repeated shape described above. It is needless to say that θmay be 0° if the moire is not generated. For the same reason, it ispreferable to make the size of the repeated shape larger than the sizeof the first sensing portion 72 a (or the first sensing portion 72 b).

The output image data ImgOut, the first image data, and the second imagedata that are generated are used in forming the output of the thin metalwire 16. For example, when producing the conductive sheets 10 and 11using exposure, the output image data ImgOut, the first image data, andthe second image data are used to make the pattern of the photomask.When producing the conductive sheets 10 and 11 by printing includingscreen printing and ink jet printing, the output image data ImgOut, thefirst image data, and the second image data are used as printing data.

Next, as a method for forming the first conductive pattern 70 a, thefirst dummy pattern 76 a, and the second conductive pattern 70 b(hereinafter, may be referred to as the first conductive pattern 70 a orthe like), for example, a method may be employed in which aphotosensitive material having an emulsion layer containingphotosensitive silver halide on the transparent base 12 is exposed anddevelopment processing is performed on the resultant to form a metalsilver portion and a light-transmissive portion corresponding to anexposed portion and an unexposed portion, respectively, thereby formingthe first conductive pattern 70 a and the like. Further, the metalsilver portion may be caused to carry conductive metal by performingphysical development and/or plating processing on the metal silverportion. A production method shown below can be preferably adopted forthe conductive sheet 11 shown in FIG. 2B. That is, in the method, byperforming one-shot exposure on the photosensitive silver halideemulsion layers formed on both surfaces of the transparent base 12, thefirst conductive pattern 70 a and the first dummy pattern 76 a areformed on one main surface of the transparent base 12, and the secondconductive pattern 70 b is formed on the other main surface of thetransparent base 12.

A specific example of this conductive sheet producing method will bedescribed with reference to FIGS. 35 to 37.

First, in step S10 of FIG. 35, image data provided to form an output ofthe mesh pattern 20 is generated. This step is performed according tothe flowchart of FIG. 27. That is, in the steps of generating the outputimage data, image data representing the design of a mesh patternobtained by arraying different mesh shapes is generated, an evaluationvalue is calculated by quantifying the degree of variation of thecentroid position of each mesh shape on the basis of the generated imagedata, and a piece of image data is determined as output image data onthe basis of the calculated evaluation value and predeterminedevaluation conditions. Since the specific method has already beendescribed above, the explanation herein will be omitted.

Hereinafter, in plan view, described in detail is the process forobtaining a conductive sheet, in which a mesh pattern is formed on abase by outputting and forming a conductive wire on the base inaccordance with the output image data determined as described above.

In step S102 of FIG. 35, a long photosensitive material 140 is prepared.As shown in FIG. 36A, the photosensitive material 140 includes atransparent base 12, a photosensitive silver halide emulsion layerformed on one main surface of the transparent base 12 (hereinafter,referred to as a first photosensitive layer 142 a), and a photosensitivesilver halide emulsion layer formed on the other main surface of thetransparent base 12 (hereinafter, referred to as a second photosensitivelayer 142 b).

The photosensitive material 140 is exposed in step S103 of FIG. 35. Inthis exposure processing, a first exposure processing for the firstphotosensitive layer 142 a in which the first photosensitive layer 142 ais exposed along the first exposure pattern by irradiating light towardthe transparent base 12 and a second exposure processing for the secondphotosensitive layer 142 b in which the second photosensitive layer 142b is exposed along the second exposure pattern by irradiating lighttoward the transparent base 12 are performed (double-sided simultaneousexposure). In the example shown in FIG. 36B, the first light 144 a(parallel light) is irradiated to the first photosensitive layer 142 athrough a first photomask 146 a and second light 144 b (parallel light)is irradiated to the second photosensitive layer 142 b through a secondphotomask 146 b while transporting the long photosensitive material 140in one direction. The first light 144 a is obtained by converting lightemitted from a first light source 148 a into parallel light using afirst collimator lens 150 a en route, and the second light 144 b isobtained by converting light emitted from a second light source 148 binto parallel light using a second collimator lens 150 b en route.

In the example shown in FIG. 36B, a case is shown in which two lightsources (first and second light sources 148 a and 148 b) are used.However, light emitted from one light source may be divided through anoptical system, and the respective lights divided may be irradiated tothe first and second photosensitive layers 142 a and 142 b as the firstlight 144 a and the second light 144 b.

Then, in step S104 of FIG. 35, the photosensitive material 140 afterexposure is developed. Since the exposure time and development time ofthe first and second photosensitive layers 142 a and 142 b variouslychange depending on the type of the first and second light sources 148 aand 148 b, the type of developer, and the like, the preferable numericalrange cannot be categorically determined. However, the exposure time andthe development time are adjusted so as to realize the development rateof 100%.

In the first exposure processing of the production method according tothe present embodiment, as shown in FIG. 37, the first photomask 146 ais disposed on the first photosensitive layer 142 a so as to be broughtinto close contact with each other, for example, and the first light 144a is irradiated from the first light source 148 a, which is disposed soas to face the first photomask 146 a, toward the first photomask 146 ato expose the first photosensitive layer 142 a. The first photomask 146a is configured to include a glass substrate formed of transparent sodaglass and a mask pattern (first exposure pattern 152 a) formed on theglass substrate. Therefore, a portion along the first exposure pattern152 a formed on the first photomask 146 a, of the first photosensitivelayer 142 a, is exposed by the first exposure processing. A spacing ofabout 2 μm to 10 μm may be provided between the first photosensitivelayer 142 a and the first photomask 146 a.

Similarly, in the second exposure processing, the second photomask 146 bis disposed on the second photosensitive layer 142 b so as to be broughtinto close contact with each other, for example, and the second light144 b is irradiated from the second light source 148 b, which isdisposed so as to face the second photomask 146 b, toward the secondphotomask 146 b to expose the second photosensitive layer 142 b. Similarto the first photomask 146 a, the second photomask 146 b is configuredto include a glass substrate formed of transparent soda glass and a maskpattern (second exposure pattern 152 b) formed on the glass substrate.Therefore, a portion along the second exposure pattern 152 b formed onthe second photomask 146 b, of the second photosensitive layer 142 b, isexposed by the second exposure processing. In this case, a spacing ofabout 2 μm to 10 μm may be provided between the second photosensitivelayer 142 b and the second photomask 146 b.

In the first exposure processing and the second exposure processing, theirradiation timing of the first light 144 a from the first light source148 a and the irradiation timing of the second light 144 b from thesecond light source 148 b may be the same or may be different. If boththe irradiation timings are the same, it is possible to reduce theprocessing time since the first and second photosensitive layers 142 aand 142 b can be exposed simultaneously by one exposure processing.

Finally, in step S105 of FIG. 35, the conductive sheet 11 is completedby performing lamination processing on the photosensitive material 140after the development processing. Specifically, the first protectivelayer 26 a is formed on the first photosensitive layer 142 a side, andthe second protective layer 26 b is formed on the second photosensitivelayer 142 b side. These protect the first and second sensor portions 60a and 60 b.

In this way, electrodes of the touch panel 44 can be easily formed byusing the production method employing the aforementioned double-sidedone-shot exposure. As a result, it is possible to make the touch panel44 thin (have a low profile).

Although the example described above is a production method for formingthe first conductive pattern 70 a and the like using a photosensitivesilver halide emulsion layer, there are the following production methodsas other production methods.

For example, the first conductive pattern 70 a and the like may beformed by exposing and developing a photoresist film on a copper foil,which is formed on the transparent base 12, to form a resist pattern andetching the copper foil exposed from the resist pattern. Alternatively,the first conductive pattern 70 a and the like may be formed by printingpaste containing metal particulates on the transparent base 12 andperforming metal plating on the paste. Alternatively, the firstconductive pattern 70 a and the like may be printed and formed on thetransparent base 12 by using a screen printing plate or a gravureprinting plate. Alternatively, the first conductive pattern 70 a and thelike may be formed on the transparent base 12 using an ink jet.

Subsequently, modifications (first to fifth modifications) of theconductive sheet 11 according to the present embodiment will bedescribed with reference to FIGS. 38 to 44. In the modifications, thesame reference numerals as those in the present embodiment are given tothe same components as those in the present embodiment, and detailedexplanation thereof will be omitted.

[First Modification]

A touch panel 160 may be of a resistance film type (and further, adigital type and an analog type) instead of a capacitive type.Hereinafter, the structure and the principle of operation will bedescribed with reference to FIGS. 38 to 40.

The digital resistance film type touch panel 160 includes a lower panel162, an upper panel 164 disposed so as to face the lower panel 162, anadhesive frame layer 166 that bonds the lower and upper panels 162 and164 together at the edges of those and electrically insulates the lowerand upper panels 162 and 164 from each other, and a flexible printedcircuit (FPC) 168 interposed between the lower and upper panels 162 and164.

As shown in FIGS. 38 and 39A, the upper panel 164 includes a firsttransparent base 170 a formed of a flexible material (for example,resin) and a first sensor portion 172 a and a first terminal wiringportion 174 a that are formed on one main surface (arrow Z2 directionside) of the first transparent base 170 a. The first sensor portion 172a includes two or more first conductive patterns 176 a formed by aplurality of thin metal wires 16. The belt-like first conductivepatterns 176 a extend in the arrow Y direction, and are arrayed at equalintervals in the arrow X direction. Each of the first conductivepatterns 176 a is electrically connected to the FPC 168 through thefirst terminal wiring portion 174 a. Between the first conductivepatterns 176 a, a belt-like first dummy pattern 178 a is disposed.

As shown in FIGS. 38 and 39B, the lower panel 162 includes a secondtransparent base 170 b formed of a high-rigidity material (for example,glass), a second sensor portion 172 b and a second terminal wiringportion 174 b that are formed on one main surface (arrow Z1 directionside) of the second transparent base 170 b, and a number of dot spaces180 disposed at predetermined intervals on the second sensor portion 172b. The second sensor portion 172 b includes two or more secondconductive patterns 176 b formed by a plurality of thin metal wires 16.The belt-like second conductive patterns 176 b extend in the arrow Xdirection, and are arrayed at equal intervals in the arrow Y direction.Each of the second conductive patterns 176 b is electrically connectedto the FPC 168 through the second terminal wiring portion 174 b. Betweenthe second conductive patterns 176 b, a belt-like second dummy pattern178 b is disposed.

As shown in FIGS. 38 and 40, in a state where the upper and lower panels164 and 162 are bonded together, the first sensor portion 172 a isdisposed so as to be spaced apart from the second sensor portion 172 bby a predetermined distance through each dot spacer 180. In addition, anumber of approximately square overlapping regions 182 are formed bymaking the first and second conductive patterns 176 a and 176 b crosseach other. Further, each dot spacer 180 is disposed at a position wherethe first and second dummy patterns 178 a and 178 b cross each other.That is, a positional relationship is established in which one dotspacer 180 is disposed in each of the four corners of each overlappingregion 182.

Next, the operation of a touch panel 160 will be described. In responseto pressure from the input surface (main surface of the firsttransparent base 170 a on the arrow Z1 side), the flexible firsttransparent base 170 a is bent concavely. Then, a part of the firstconductive pattern 176 a is brought into contact with a part of thesecond conductive pattern 176 b in a portion that corresponds to oneoverlapping region 182 surrounded by four dot spacers 180 and closest tothe pressing position. Under this condition, by applying a voltagethrough the FPC 168, a potential gradient is generated between the upperand lower panels 164 and 162. That is, an input position in the arrow Xdirection (X axis) can be detected by reading a voltage from the upperpanel 164 through the FPC 168. Similarly, an input position in the arrowY direction (Y axis) can be detected by reading a voltage from the lowerpanel 162.

Here, the width w3 of the first conductive pattern 176 a (or the secondconductive pattern 176 b) may be variously set according to theresolution. For example, about 1 mm to 5 mm is preferable. The width w4of the first dummy pattern 178 a (or the second dummy pattern 178 b) ispreferably in a range of 50 μm to 200 μm in terms of insulation from thefirst conductive pattern 176 a (or the second conductive pattern 176 b)and the sensitivity of the touch panel 160.

The structure of the mesh pattern 20 shown in FIG. 2A appears when partsof the single hatched regions (first and second conductive patterns 176a and 176 b) and the double hatched regions (first and second dummypatterns 178 a and 178 b), which are shown in FIGS. 39A and 39B, areenlarged. That is, it is preferable to determine the wiring shape bywhich both of the suppression of moire generation and the reduction ofgranular feeling of noise can be realized under the state in which theupper and lower panels 164 and 162 are superimposed.

[Second Modification]

The contour shape of a first conductive pattern 192 a and/or a secondconductive pattern 192 b may be different from the shape in the presentembodiment. Hereinafter, first and second sensor portions 190 a and 190b having an approximately lattice-shaped pattern macroscopically in planview, without forming the first sensing portion 72 a (refer to FIG. 5A)and the second sensing portion 72 b (refer to FIG. 5B), will bedescribed with reference to FIGS. 41A and 41B.

FIG. 41A is a partially enlarged view of the first sensor portion 190 a(the first conductive portion 14 a and the first dummy electrode portion15 a), and FIG. 41B is a partially enlarged view of the second sensorportion 190 b (the second conductive portion 14 b and the second dummyelectrode portion 15 b). For the convenience of explanation, in FIGS.41A and 41B, only the contour of the mesh pattern 20 formed by aplurality of thin metal wires 16 is shown in a single line. That is,when a part of each single line shown in FIGS. 41A and 41B is enlarged,the structure of the mesh pattern 20 shown in FIG. 2A appears.

As shown in FIG. 41A, two or more first conductive patterns 192 a formedby a plurality of thin metal wires 16 are provided in a portioncorresponding to the first sensor portion 190 a. The first conductivepatterns 192 a extend in the arrow Y direction, and are arrayed at equalintervals in the arrow X direction perpendicular to the arrow Ydirection. The first conductive pattern 192 a is different from thesecond conductive pattern 70 b (refer to FIG. 5B), and has anapproximately constant line width. Between the first conductive patterns192 a, a lattice-shaped first dummy pattern 194 is disposed. The firstdummy pattern 194 is configured to include four long line patterns 196,which extend in the arrow Y direction and are disposed at equalintervals, and a number of short line patterns 198, which are disposedso as to cross the four long line patterns 196. The short line patterns198 have the same length, and are disposed at equal intervals in thearrow Y direction with the four short line patterns 198 as a unit.

As shown in FIG. 41B, two or more second conductive patterns 192 bformed by a plurality of thin metal wires 16 are provided in a portioncorresponding to the second sensor portion 190 b. The second conductivepatterns 192 b extend in the arrow X direction, and are arrayed at equalintervals in the arrow Y direction perpendicular to the arrow Xdirection. The second conductive pattern 192 b is different from thefirst conductive pattern 70 a (refer to FIG. 5A), and has anapproximately constant line width. Between the second conductivepatterns 192 b, a number of linear second dummy patterns 200 extendingin the arrow X direction are disposed. The second dummy patterns 200 allhave the same length, and are disposed at equal intervals in the arrow Ydirection with the four second dummy patterns 200 as a unit.

That is, the designs formed in the first sensor portion 190 a (refer toFIG. 41A) and the second sensor portion 190 b (refer to FIG. 41B)complement each other in plan view, and a lattice shape having a unitdefined by a lattice element 202 is completed. Even with thisconfiguration, the same effects as the present invention can beobtained.

[Third Modification]

A conductive sheet 210 may be formed by two sheet members (first andsecond sheet members 212 a and 212 b).

As shown in FIG. 42, the conductive sheet 210 is formed by laminatingthe second sheet member 212 b and the first sheet member 212 a in orderfrom the lower side. The first sheet member 212 a includes a firstconductive portion 14 a and a first dummy electrode portion 15 a thatare formed on one main surface (arrow s1 direction side) of a firsttransparent base 12 a. The second sheet member 212 b includes a secondconductive portion 14 b formed on one main surface (arrow s1 directionside) of a second transparent base 12 b. That is, it can be said thatthe first conductive portion 14 a and the like are formed on one mainsurface (arrow s1 direction side) of the first transparent base 12 a andthe second conductive portion 14 b and the like are formed on the othermain surface (arrow s2 direction side) of the first transparent base 12a.

Even if the conductive sheet 210 is formed in this manner, the sameeffects as in the present embodiment are obtained. In addition, anotherlayer may be interposed between the first and second sheet members 212 aand 212 b. Further, as long as the first and second conductive portions14 a and 14 b are insulated from each other or the first dummy electrodeportion 15 a and the second conductive portion 14 b are insulated fromeach other, they may be disposed so as to face each other.

[Fourth Modification]

A dummy electrode portion (first and second dummy electrode portions 15a and 15 b) may be provided not only on one surface of the conductivesheet 220 but also on both surfaces thereof.

As shown in FIG. 43, not only the second conductive portion 14 b butalso the second dummy electrode portion 15 b is formed on the other mainsurface (arrow s2 direction side) of the transparent base 12. Here, thesecond dummy electrode portion 15 b is disposed so as to be spaced apartfrom the second conductive portion 14 b by a predetermined distance.That is, the second dummy electrode portion 15 b is in a state where itis electrically insulated from the second conductive portion 14 b.

Thus, by providing a dummy electrode portion on both surfaces of thetransparent base 12, the effects of the present invention can beobtained in either case of arranging the conductive sheet 220 frontwardand backward when mounting the conductive sheet 220 into the displaydevice 40 (refer to FIG. 4). On the contrary, in terms of productioncost, it is also possible to adopt a configuration in which no dummyelectrode portion is provided on either surface of the transparent base12.

[Fifth Modification]

The conductive sheet 230 may have an anisotropic mesh pattern 232.

FIG. 44 is a partially enlarged plan view of the conductive sheet 230having the mesh pattern 232, the shape of the conductive sheet 230 beingoptimized under the conditions in which the black matrices 34 aresuperimposed (refer to FIG. 3).

As is understood from FIGS. 10A and 44, the design of the mesh pattern232 (each opening 18) is a horizontally long shape in general, comparedwith the design of the mesh pattern 20. The reason thereof is estimatedas follows.

When the red subpixel 32 r, the green subpixel 32 g, and the bluesubpixel 32 b are disposed in the arrow X direction as shown in FIG. 3,one pixel 32 is divided into respective ⅓ regions. Accordingly, thenoise granularity of the high spatial frequency component increases. Onthe other hand, in the arrow Y direction, only a spatial frequencycomponent equivalent to the arrangement period of the black matrix 34 ispresent, and there are no other spatial frequency components.Accordingly, the design of the mesh pattern 232 is determined so as toreduce the visibility of the arrangement period. That is, wiring linesextending in the arrow Y direction are made such that the distancebetween the wiring lines is as narrow as possible and the wiring linesare regularly disposed between the black matrices 34.

As described above, it is possible to optimize the mesh pattern 232 inconsideration of the design of the structure pattern including the blackmatrix 34. That is, the granular feeling of noise is reduced at the timeof observation in the actual use mode, and the visibility of an objectfor observation is greatly improved. This is particularly effective whenthe actual use mode of the conductive sheet 230 is known.

Next, explanation will be given focusing on a production method using asilver halide photosensitive material, which is particularly apreferable mode in the conductive sheets 10 and 11 according to thepresent embodiment.

The method for producing the conductive sheets 10 and 11 according tothe present embodiment includes the following three modes depending onthe form of a photosensitive material and development processing.

(1) Mode in which a black-and-white photosensitive silver halidephotosensitive material not containing physical development nuclei ischemically developed or thermally developed to form a metal silverportion on the photosensitive material.

(2) Mode in which a black-and-white photosensitive silver halidephotosensitive material containing physical development nuclei in asilver halide emulsion layer is dissolved and physically developed toform a metal silver portion on the photosensitive material.

(3) Mode in which a black-and-white photosensitive silver halidephotosensitive material not containing physical development nuclei andan image receiving sheet having a non-photosensitive layer containingphysical development nuclei are made to overlap each other and diffusiontransfer development is performed to form a metal silver portion on thenon-photosensitive image receiving sheet.

The mode of (1) is an integrated black-and-white development type, and atranslucent conductive film is formed on the photosensitive material.Developed silver obtained is chemically developed silver or thermallydeveloped silver, and its activity is high in the subsequent plating orphysical development processing in that it is a filament of highspecific surface.

In the mode of (2), in an exposed portion, silver halide particles nearthe physical development nuclei are dissolved and deposited on thedevelopment nuclei, and accordingly, a translucent conductive film, suchas a light-transmissive conductive film, is formed on the photosensitivematerial. This is also an integrated black-and-white development type.Since the developing action is a deposition on the physical developmentnuclei, developed silver is highly active, but has a spherical shape oflow specific surface.

In the mode of (3), silver halide particles in an unexposed portion aredissolved and diffused to be deposited on the development nuclei on theimage receiving sheet, and accordingly, a translucent conductive film,such as a light-transmissive conductive film, is formed on the imagereceiving sheet. This is a so-called a separate type, and the imagereceiving sheet is used by being peeled from the photosensitivematerial.

In any of the modes, it is possible to select any development processingof the negative type development processing and the reversal developmentprocessing (in the case of a diffusion transfer method, the negativetype development processing becomes possible by using an auto-positivetype photosensitive material as the photosensitive material).

Chemical development, thermal development, dissolution physicaldevelopment, and diffusion transfer development referred to herein aretypically the terms that are used in the art, and are explained ingeneral textbooks of photographic chemistry, for example,“Photochemistry” written by Shinichi Kikuchi (Kyoritsu Publishing Co.,published in 1955) and “The Theory of Photographic Processes, 4th ed.”written by C. E. K. Mees (Mcmillan, Inc. published in 1977). This caseis an invention related to liquid processing, but as other developmentmethods, techniques for applying the thermal development method can alsobe referred to. For example, it is possible to apply the techniquesdisclosed in JP 2004-184693 A, JP 2004-334077 A, and JP 2005-01.0752 Aand the techniques disclosed in the specifications of Japanese PatentApplication Nos. 2004-244080 and 2004-085655.

Here, the configuration of each layer of the conductive sheets 10 and 11according to the present embodiment will be described in detail below.

[Transparent Base 12]

As the transparent base 12, a plastic film, a plastic plate, a glassplate, and the like can be mentioned.

As materials of the plastic film and the plastic plate described above,it is possible to use polyesters including polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), polymethylmethacrylate (PMMA),polypropylene (PP), polystyrene (PS), and triacetyl cellulose (TAC), forexample.

As the transparent base 12, a plastic film or a plastic plate having amelting point of about 290° C. or lower is preferable. In particular, interms of optical transparency, workability, or the like, PET ispreferable.

[Silver Salt Emulsion Layer]

A silver salt emulsion layer serving as the thin metal wire 16 of eachof the first and second laminate portions 28 a and 28 b contains notonly silver salt and binder but also additives such as solvent or dye.

<1. Silver Salt>

As silver salts used in the present embodiment, inorganic silver saltssuch as silver halides and organic silver salts such as silver acetatecan be mentioned. In the present embodiment, it is preferable to usesilver halides which are excellent in characteristics as an opticalsensor.

The coating amount of silver (coating amount of silver salt) in thesilver salt emulsion layer is preferably 1 g/m² to 30 g/m², morepreferably 1 g/m² to 25 g/m², and still more preferably 5 g/m² to 20g/m², in terms of silver. By setting the coating amount of silver tofall within the above range, it is possible to cause the conductivesheets 10 and 11 to have a desired surface resistance.

<2. Binder>

As binders used in the present embodiment, for example, gelatin,polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polysaccharidessuch as starch, cellulose and its derivatives, polyethylene oxide,polyvinyl amine, chitosan, polylysine, polyacrylic acid, polyalginicacid, poly hyaluronic acid, carboxymethyl cellulose, and the like can bementioned. These have neutral, anionic, and cationic propertiesdepending on the ionicity of the functional group.

The content of the binder contained in the silver salt emulsion layer ofthe present embodiment is not limited in particular, and can beappropriately determined in a range where dispersibility andadhesiveness can be exhibited. As the content of the binder in thesilver salt emulsion layer, 1/4 or more is preferable, and 1/2 or moreis more preferable, in terms of silver/binder volume ratio. Thesilver/binder volume ratio is preferably 100/1 or less, and 50/1 or lessis more preferable. The silver/binder volume ratio of 1/1 to 4/1 isstill more preferable. Most preferably, the silver/binder volume ratiois 1/1 to 3/1. By setting the silver/binder volume ratio in the silversalt emulsion layer to fall within the above range, it is possible tosuppress a variation in the resistance value even if the coating amountof silver is adjusted. Therefore, it is possible to obtain theconductive sheet 10 having a uniform surface resistance. Thesilver/binder volume ratio can be calculated by converting the silversalt amount/binder amount of materials (ratio by weight) into the silveramount/binder amount (ratio by weight) and then converting the silveramount/binder amount (ratio by weight) into the silver amount/binderamount (volume ratio).

<3. Solvent>

The solvent used to prepare the silver salt emulsion layer is notparticularly limited. For example, water, organic solvents (for example,alcohols such as methanol, ketones such as acetone, amides such asformamide, sulfoxides such as dimethyl sulfoxide, esters such as ethylacetate, and ethers), ionic liquids, and mixture solvents of these canbe mentioned.

<4. Other Additives>

As various additives used in the present embodiment, known additives canbe preferably used without being particularly limited.

[First and Second Protective Layers 26 a and 26 b]

As the first and second protective layers 26 a and 26 b, similarly tothe transparent base 12, a plastic film, a plastic plate, a glass plate,and the like can be mentioned. As materials of the plastic film and theplastic plate described above, for example, it is possible to use PET,PEN, PM-MIA, PP, PS, TAC, and the like.

The thickness of each of the first and second protective layers 26 a and26 b is not particularly limited, and can be appropriately selecteddepending on the purpose. For example, 5 μm to 100 μm is preferable, 8μm to 50 μm is more preferable, and 10 μm to 30 μm is particularlypreferable.

Next, each of the steps of the method for producing the conductivesheets 10 and 11 will be described.

[Exposure]

In the present embodiment, the case is included in which the firstconductive portion 14 a, the second conductive portion 14 b, the firstdummy electrode portion 15 a, and the like are formed using a printingmethod. However, except for the printing method, the first conductiveportion 14 a, the second conductive portion 14 b, the first dummyelectrode portion 15 a, and the like are formed by exposure,development, and the like. That is, exposure is performed on aphotosensitive material having a silver salt-containing layer providedon the transparent base 12 or performed on a photosensitive materialcoated with photopolymer for photolithography. Exposure can be performedusing electromagnetic waves. As electromagnetic waves, for example,lights such as visible light and ultraviolet light and radiations suchas X-ray can be mentioned. For exposure, a light source having awavelength distribution may be used, or a light source of a specificwavelength may be used.

[Development Processing]

In the present embodiment, development processing is further performedafter exposing the emulsion layer. The development processing can beperformed using the technique of normal development processing used forsilver halide photographic films, photographic papers, films forprinting plate, emulsion masks for photomask, and the like.

The development processing in the present invention can include fixingprocessing that is performed for the purpose of stabilization byremoving the silver salt of an unexposed portion. The fixing processingin the present invention can be performed using the technique of fixingprocessing used for silver halide photographic films, photographicpapers, films for printing plate, emulsion masks for photomask, and thelike.

It is preferable to perform washing processing or stabilizationprocessing on the photosensitive material subjected to the developmentprocessing and the fixing processing.

The mass of a metal silver portion included in the exposed portion afterthe development processing is preferably a content of 50% by mass ormore of the mass of silver contained in the exposed portion beforeexposure, and 80% by mass or more is more preferable. If the mass ofsilver contained in the exposed portion is equal to or greater than 50%by mass of the mass of silver contained in the exposed portion beforeexposure, high conductivity can be obtained and thus it is preferable.

Through the above steps, the conductive sheets 10 and 11 are obtained.Calendering processing may be further performed on the conductive sheets10 and 11 after the development processing, and by calenderingprocessing, the surface resistance of the conductive sheets 10 and 11can be adjusted to obtain a desired surface resistance. It is preferablethat the surface resistance of the obtained conductive sheets 10 and 11be in a range of 0.1Ω/sq. to 300Ω/sq.

The surface resistance set depends on the application of the conductivesheets 10 and 11. For example, in the case of touch panel applications,1Ω/sq. to 70Ω/sq. is preferable, 5Ω/sq. to 50Ω/sq. is more preferable,and 5Ω/sq. to 30Ω/sq. is still more preferable. In the case ofelectromagnetic wave shielding applications, 10Ω/sq. or less ispreferable, and 0.1Ω/sq. to 3Ω/sq. is more preferable.

[Physical Development and Plating Processing]

In the present embodiment, in order to improve the conductivity of themetal silver portion formed by the exposure and development processingdescribed above, physical development and/or plating processing forcausing the metal silver portion to carry conductive metal particles maybe performed. In the present invention, conductive metal particles maybe carried on the metal silver portion by either physical development orplating processing, or conductive metal particles may be carried on themetal silver portion by combination of physical development and platingprocessing. A metal silver portion after being subjected to physicaldevelopment and/or plating processing is referred to as a “conductivemetal portion”.

The “physical development” in the present embodiment refers todepositing metal particles on nuclei of metal or metal compound byreducing metal ions, such as silver ions, with a reducing agent. Thisphysical development is used for an instant B&W film, an instant slidefilm, printing plate production, and the like, and in the presentinvention, it is possible to use the technique. The physical developmentmay be performed simultaneously with development processing afterexposure, or may be separately performed after development processing.

In the present embodiment, as the plating processing, it is possible touse an electroless plating (chemical reduction plating or displacementplating), an electroplating, or both the electroless plating andelectroplating. As electroless plating in the present embodiment, it ispossible to use known electroless plating techniques. For example, it ispossible to use an electroless plating technique used for a printedwiring board and the like. The electroless plating is preferably anelectroless copper plating.

In the method for producing the conductive sheets 10 and 11 according tothe present embodiment, steps, such as plating and the like, do notnecessarily need to be performed. This is because a desired surfaceresistance can be obtained by adjusting the coating amount of silver inthe silver salt emulsion layer and the silver/binder volume ratio in thepresent production method.

[Oxidation Processing]

In the present embodiment, it is preferable to perform oxidationprocessing on the metal silver portion after the development processingand the conductive metal portion formed by physical development and/orplating processing. By performing oxidation processing, for example,when metal is slightly deposited on a light-transmissive portion, it ispossible to remove the metal so that the transmittance of thelight-transmissive portion becomes approximately 100%.

[Film Hardening Processing after Development Processing]

After performing development processing on the silver salt emulsionlayer, it is preferable to perform hardening processing by immersing theresultant in the hardening agent. As the hardening agent, for example,glutaraldehyde, adipaldehyde, dialdehydes such as2,3-dihydroxy-1,4-dioxane, and boric acid disclosed in JP 2-141279 A canbe mentioned.

A functional layer, such as an antireflection layer or a hard coatlayer, may be given to the conductive sheets 10 and 11 according to thepresent embodiment.

[Calendering Processing]

The metal silver portion after the development processing may besmoothed by performing calendering processing. By the calenderingprocessing, the conductivity of the metal silver portion is noticeablyincreased. The calendering processing can be performed using a calenderroll. Usually, the calender roll includes a pair of rolls.

As rolls for the calendering processing, metal rolls or plastic rollsmade of resin such as epoxy, polyimide, polyamide, and polyimidoamide,are used. In particular, when an emulsion layer is provided on bothsurfaces, it is preferable to perform calendaring processing using apair of metal rolls. When an emulsion layer is provided on one surface,a combination of a metal roll and a plastic roll may be used in terms ofanti-wrinkling. The lower limit of linear pressure is equal to orgreater than 1960 N/cm (200 kgf/cm; when converted into surfacepressure, 699.4 kgf/cm²), and more preferably equal to or greater than2940 N/cm (300 kgf/cm; when converted into surface pressure, 935.8kgf/cm²). The upper limit of linear pressure is equal to or less than6880 N/cm (700 kgf/cm).

Preferably, the application temperature of smoothing processingrepresented by the calender roll is 10° C. (no temperature control) to100° C. The more preferable temperature is in a range of 10° C. (notemperature control) to 50° C. although it changes depending on thewiring density or shape of the metal mesh pattern or the metal wiringpattern and the binder type.

[Lamination Processing]

In order to protect the first and second sensor portions 60 a and 60 b,a protective layer may be formed on the silver salt emulsion layer.Adjustment of adhesiveness can be freely performed by providing thefirst adhesive layer 24 a (or the second adhesive layer 24 b) betweenthe protective layer and the silver salt emulsion layer.

As materials of the first and second adhesive layers 24 a and 24 b, wetlaminate adhesives, dry laminate adhesives, or hot melt adhesives can bementioned. In particular, dry laminate adhesives, by which many kinds ofmaterials can be bonded and which have high bonding speed, arepreferable. Specifically, amino resin adhesives, phenolic resinadhesives, chloroprene rubber adhesives, nitrile rubber adhesives, epoxyadhesives, urethane adhesives, reaction type acrylic adhesives, and thelike can be used as dry laminate adhesives. Among these adhesives, it ispreferable to use OCA (Optical Clear Adhesive; registered trademark)manufactured by Sumitomo 3M Limited, which is an acrylic adhesive havinga low acid value.

As drying conditions, a temperature environment of 30° C. to 150° C. and1 minute to 30 minutes are preferable. A drying temperature of 50° C. to120° C. is particularly preferable.

Instead of providing the adhesive layer described above, the interlayeradhesive force can be adjusted by performing surface treatment on atleast one of the transparent base 12 and the protective layer. In orderto increase the adhesive force with respect to the silver salt emulsionlayer described above, for example, corona discharge treatment, flametreatment, ultraviolet irradiation treatment, high-frequency radiationtreatment, glow discharge irradiation treatment, active plasmairradiation treatment, laser beam irradiation treatment, and the likemay be performed.

The present invention can be used by being appropriately combined withthe techniques disclosed in Japanese Unexamined Patent ApplicationPublications and International Publication Pamphlets respectively listedin the following Tables 1 and 2. Notations of “JP”, “A”, “Pamphlet”, andthe like are omitted.

TABLE 1 2004-221564 2004-221565 2007-200922 2006-352073 2007-1292052007-235115 2007-207987 2006-012935 2006-010795 2006-228469 2006-3324592009-21153 2007-226215 2006-261315 2007-072171 2007-102200 2006-2284732006-269795 2006-269795 2006-324203 2006-228478 2006-228836 2007-0093262006-336090 2005-336099 2006-348351 2007-270321 2007-270322 2007-2013782007-335729 2007-134439 2007-149760 2007-208133 2007-178915 2007-3343252007-310091 2007-116137 2007-088219 2007-207883 2007-013130 2005-3025082008-218784 2008-227350 2008-227351 2008-244067 2008-267814 2008-2704052008-277675 2008-277676 2008-282840 2008-283029 2008-288305 2008-2884192008-300720 2008-300721 2009-4213 2009-10001 2009-16526 2009-213342009-26933 2008-147507 2008-159770 2008-159771 2008-171568 2008-1983882008-218096 2008-218264 2008-224916 2008-235224 2008-235467 2008-2419872008-251274 2008-251275 2008-252046 2008-277428

TABLE 2 2006/001461 2006/088059 2006/098333 2006/098336 2006/0983382006/098335 2006/098334 2007/001008

EXAMPLES

Hereinafter, the present invention will be described more specificallyby way of examples of the present invention. In the present invention,materials, amounts, ratios, processings, processing procedures, and thelike shown in the following examples can be appropriately modifiedwithout departing from the gist of the present invention. Therefore, thescope of the present invention should not be construed as being limitedby the examples shown below.

The surface resistivity, visibility (granular feeling of noise), andbrightness change rate in the display device 40 including the conductivesheet 11 of examples 1 to 1.3, comparative examples 1 to 3, andreference examples 1 to 4 were evaluated.

Examples 1 to 13, Comparative Examples 1 to 3, and Reference Examples 1to 4 Silver halide photosensitive material

An emulsion containing iodobromochloride silver particles (I=0.2 mol %,Br=40 mol %) having an average sphere-equivalent diameter of 0.1 μm wasprepared. The emulsion contained gelatin of 10.0 g with respect to Ag of150 g in an aqueous medium.

K₃Rh₂Br₉ and K₂IrCl₆ were added to the emulsion so that theconcentration became 10⁻⁷ (mol/mol Ag) to dope silver bromide particleswith Rh ions and Ir ions. Na₂PdCl₄ was added to the emulsion andfurther, the emulsion was subjected to gold-sulfur sensitization usingchloroauric acid and sodium thiosulfate.

Then, together with a gelatin hardening agent, the emulsion was coatedon a transparent base (here, polyethylene terephthalate (PET) having arefractive index of n0=1.64) so that the coating amount of silver became10 g/m². In this case, the Ag/gelatin volume ratio was set to 2/1.

The emulsion was coated on the PET support having a width of 300 mm soas to have a coating width of 250 mm for 20 m, and each of both ends ofthe support was cut by 30 mm each so that 240 mm of the central portionof the coating width was left, thereby a roll-shaped silver halidephotosensitive material was obtained.

(Generation of an Exposure Pattern)

Using the SA method (refer to FIG. 27 and the like) described in thepresent embodiment, the output image data ImgOut representing the meshpattern 20 (refer to FIG. 2A) which was filled with the polygonal meshshapes 22 without space, was generated.

As the preparation conditions of the mesh pattern 20, the totaltransmittance, the thickness of the transparent base 12, the width ofthe thin metal wire 16, and the thickness of the thin metal wire 16 wereset to 93%, 20 μm, 20 μm, and 10 μm, respectively. The size of the unitregion 90 in both the horizontal and vertical directions was 5 mm, andthe image resolution thereof was 3500 dot per inch (dpi). The initialposition of the seed point SD was randomly determined using the Mersennetwister, and each mesh shape 22 of the polygonal shape was determinedaccording to the Voronoi diagram. By regularly arranging the unit imagedata ImgE using the method shown in FIGS. 30 and 31, the output imagedata ImgOut having a repeated shape was formed. It was confirmed laterthat the desired conductive sheet 11 was produced by the output imagedata ImgOut.

Then, as shown in FIGS. 34A and 34B, a first exposure pattern includinga region excluding the first region R1 and a second exposure patternincluding the second region R2 were prepared by cutting out the wiringshape in the planar region 100.

For comparison, exposure patterns representing the patterns PT1 to PT3(refer to FIGS. 46A to 46C) according to the conventional examples werealso generated. These are referred to as comparative examples 1 to 3.

Meanwhile, by changing the value of the coefficient αj (j 1 and 2)variously for the evaluation value EVP shown in Expression (5), ninetypes of mesh patterns 20 having different regularities (randomness) ofthe arrangement of the mesh shapes 22 were obtained. Hereinafter, theseare set as reference example 3, example 7, example 8, example 9, example10, example 11, example 12, example 13, and reference example 4 in orderof high regularity (in order of low randomness). With respect to theexamples 1 to 6 and the reference examples 1 and 2 to be describedlater, the mesh pattern 20 having the same shape as in the example 10was used.

(Exposure)

Exposure was performed on both surfaces of the transparent base 12 of A4size (210 mm×297 mm). The exposure was performed using parallel lightfrom a high-pressure mercury lamp as a light source through thephotomasks of the first exposure pattern (corresponding to the firstconductive portion 14 a side) and the second exposure pattern(corresponding to the second conductive portion 14 b side) describedabove.

(Development Processing)

Formulation of Developer 1L:

hydroquinone 20 g

sodium sulfite 50 g

potassium carbonate 40 g

ethylenediaminetetraacetic acid 2 g

potassium bromide 3 g

polyethylene glycol 2000 1 g

potassium hydroxide 4 g

adjusted to pH 10.3

Formulation of Fixer 1L:

ammonium thiosulfate liquid (75%) 300 ml

Ammonium sulfite monohydrate 25 g

1,3-diaminopropane tetraacetic acid 8 g

acetic acid 5 g

aqueous ammonia (27%) 1 g

adjusted to pH 6.2

Using the processing agent described above, the exposed photosensitivematerial was processed under the processing conditions (development: 35°C., 30 seconds, fixation: 34° C., 23 seconds, and washing water flow: 5L/minute, 20 seconds) using an automatic developing machine FG-710PTSmanufactured by Fuji Photo Film Co., Ltd.

(Lamination Processing)

The first and second protective layers 26 a and 26 b formed of the samematerial were each bonded to the two sides of the developedphotosensitive materials, respectively. As will be described later, aprotective film having a different refractive index n1 was used for eachsample of the conductive sheet 10. In addition, a commercially availableadhesive tape (NSS50-1310; New Tac Kasei Co. Ltd., 50 μm in thickness)was used as the first adhesive layer 24 a and the second protectivelayer 26 b (refer to FIG. 2B). After bonding the first and secondprotective layers 26 a and 26 b, autoclaving of 20-minute heating underthe environment of 0.5 atmospheric pressure and 40° C. was performed inorder to prevent the generation of bubbles.

For the convenience of evaluation, the first protective layer 26 aobtained by cutting out a part of the sheet was used. That is, adifference between a case where the first protective layer 26 a wasformed (refractive index n1) and a case where the first protective layer26 a was not formed (air layer of the refractive index 1.00) could beseen at once. Hereinafter, a display portion corresponding to the cutoutportion of the first protective layer 26 a is referred to as a region“with no protective layer”, and the remaining display portion isreferred to as a region “with a protective layer”.

Example 1

The conductive sheet 11 according to the example 1 was prepared usingpolychlorotrifluoroethylene (PCTTE) having a refractive index of n1=1.42as the first protective layer 26 a. In this case, the relativerefractive index nr1 is nr1=(1.42/1.64)=0.86.

Example 2, Examples 7 to 13, Comparative Examples 1 to 3, and ReferenceExamples 3 and 4

The conductive sheet 11 according to the example 2 was prepared usingpolymethylmethacrylate (PMMA) having a refractive index of n1=1.50 asthe first protective layer 26 a. In this case, the relative refractiveindex nr1 is nr1=(1.50/1.64)=0.91.

With respect to the comparative example 1 corresponding to the patternPT1 (refer to FIG. 46A), the comparative example 2 corresponding to thepattern PT2 (refer to FIG. 46B), the comparative example 3 correspondingto the pattern PT3 (refer to FIG. 46C), the examples 7 to 13corresponding to the mesh pattern 20 (refer to FIG. 2A), and thereference examples 3 and 4, each sample coated withpolymethylmethacrylate was prepared.

Example 3

The conductive sheet 11 according to the example 3 was prepared usingpolystyrene (PS) having a refractive index of n1=0.60 as the firstprotective layer 26 a. In this case, the relative refractive index nr1is nr1=(1.60/1.64)=0.97.

Example 4

The conductive sheet 11 according to the example 4 was prepared usingpolythiourethane (PTU) having a refractive index of n1=1.70 as the firstprotective layer 26 a. In this case, the relative refractive index nr1is nr1=(1.70/1.64)=1.03.

Example 5

The conductive sheet 11 according to the example 5 was prepared usinghigh refractive index glass having a refractive index of n1=1.78 as thefirst protective layer 26 a. In this case, the relative refractive indexnr1 is nr1=(1.78/1.64)=1.08.

Example 6

The conductive sheet 11 according to the example 6 was prepared usingultra-high refractive index glass having a refractive index of n1=1.90as the first protective layer 26 a. In this case, the relativerefractive index nr1 is nr1=(1.90/1.64)=1.15.

Reference Example 1

The conductive sheet 11 according to the reference example 1 wasprepared using tetrafluoroethylene (FEP) having a refractive index ofn1=1.34 as a first protective layer. In this case, the relativerefractive index nr1 is nr1=(1.34/1.64)=0.81.

Reference Example 2

The conductive sheet 11 according to the reference example 2 wasprepared using ultra-high refractive index glass having a refractiveindex of n1=1.98 as a first protective layer. In this case, the relativerefractive index nr1 is nr1=(1.98/1.64)=1.20.

[Evaluation]

Each sample according to the examples 1 to 13, the comparative examples1 to 3, and the reference examples 1 and 2 was bonded onto the displayscreen of the display unit 30. As the display unit 30, a commerciallyavailable color liquid crystal display (11.6-inch screen size, 1366×768dots, and 192-μm pixel pitch in both the horizontal and verticaldirections) was used.

(Surface Resistance Measurement)

In order to evaluate the uniformity of the surface resistivity, thesurface resistivity of each sample of the example 2 and the comparativeexamples 1 to 3 was measured at 10 arbitrary locations using the LorestaGP (model number MCP-T610) series 4-point probe (ASP) manufactured byDia Instruments Co., and the average value was taken.

(Granular Feeling of Noise)

Under the conditions in which white color (maximum brightness) wasdisplayed by controlling the display of the display unit 30, threeresearchers performed sensory evaluation of the granular feeling ofnoise (feeling of roughness). This evaluation was digitized taking intoconsideration a feeling of noise of the brightness due to the mesh shape22 and a feeling of noise of the color due to the structure of thesubpixels comprehensively. The viewing distance from the display screenwas set to 300 mm, and the indoor illuminance was set to 300 lx.

In this sensory evaluation, comparative observation with respect to thevisual recognition result in the region “with no protective layer”(display region where the first protective layer 26 a was not formed)was performed. Specifically, 5 points were scored when the granularfeeling of noise in the region “with a protective layer” was improvedsignificantly compared with that in the region “with no protectivelayer”, 4 points were scored when it was improved, 3 points were scoredwhen there was no change, 2 points were scored when it became worse, and1 point was scored when it became worse significantly. The average valueof the point scores given by the researchers was regarded as theevaluation value of the granular feeling of noise.

(Brightness Change Rate)

Under the conditions in which white color (maximum brightness) wasdisplayed by controlling the display of the display unit 30, thebrightness on the display screen was measured. LS-100 (manufactured byKonica Minolta, Inc.) was used as the luminance meter. The measurementdistance from the display screen was set to 300 mm, the measurementangle was set to 2°, and the indoor illuminance was set to 1 lx orlower.

Assuming that the brightness in the region “with no protective layer”was La [cd/m²] and the brightness in the region “with a protectivelayer” was Lb [cd/m²], the brightness change rate (unit: %) wascalculated as 100×(Lb−La)/La. In addition, in consideration of thein-plane uniformity, a measurement position within the region “with aprotective layer” was set near the boundary of the region “with noprotective layer”.

(Relationship Between Irregularity and Visibility)

Sensory evaluation was performed in order to examine the relationshipbetween the irregularity and the visibility of the mesh pattern 20 whichwas filled with the polygonal mesh shapes 22 without space.Specifically, individual evaluations of moire, feeling of roughness andcolor noise and an overall evaluation were performed in three grades forthe samples according to the examples 7 to 13 and the reference examples3 and 4.

The case where moire was not noticeable was evaluated to be “A”, thecase where moire was viewed but caused no problems was evaluated to be“B”, and the case where moire was noticeable was evaluated to be “C”.The average of evaluations by the researchers was set as the moireevaluation result.

The case where the feeling of roughness was not noticeable was evaluatedto be “A”, the case where the feeling of roughness was viewed but causedno problems was evaluated to be “B”, and the case where the feeling ofroughness was noticeable was evaluated to be “C”. The average ofevaluations by the researchers was set as the feeling of roughnessevaluation result.

The case where color noise was not noticeable was evaluated to be “A”,the case where color noise was viewed but caused no problems wasevaluated to be “B”, and the case where color noise was noticeable wasevaluated to be “C”. The average of evaluations by the researchers wasset as the color noise evaluation result.

The case where the visibility of the display screen was good wasevaluated to be “A”, the case where any uncomfortable feeling was sensedbut the level of the visibility was sufficient was evaluated to be “B”,and the case where the visibility was poor was evaluated to be “C”. Theaverage of evaluations by the researchers was set as the visibilityevaluation result.

[Results]

(Surface Resistance Measurement)

In the example 2 and the comparative examples 1 to 3, the surfaceresistivity was at a level that could be sufficiently put to practicaluse as a transparent electrode, and translucency was also good. Inparticular, a variation in the surface resistivity was the smallest inthe example 2 (conductive sheet 11 according to the present invention).

(Granular Feeling of Noise)

[1] Regarding the visibility between the patterns, good evaluations wereobtained in order of the samples of the example 2, the comparativeexample 3, the comparative example 1, and the comparative example 2.This order is same as the order of the smallest area to the larger areasformed by the peak of the power spectrum shown in FIG. 12. Inparticular, it was confirmed that the granular feeling of noise in theexample 2 (conductive sheet 11 according to the present invention) wasnot even noticeable.

[2] As shown in FIG. 45, in the examples 1 to 6 and the referenceexamples 1 and 2, the evaluation values exceeded 3, and the reductioneffect of the granular feeling of noise was obtained by eliminating theair layer. Among them, in the examples 1 to 6, the evaluation valuesexceeded 4, and the noticeable effect was observed compared with thereference examples 1 and 2. That is, a conclusion that the granularfeeling of noise could be suppressed when the relative refractive indexnr1 satisfied the relationship of 0.86≦nr1≦1.15 was obtained.

(Brightness Change Rate)

As shown in Table 3, in the examples 1 to 6 and the reference examples 1and 2, the brightness change rate was a positive value, and thebrightness on the display screen was improved by eliminating the airlayer (air gap).

TABLE 3 Brightness change rate (%) Reference 15.1 example 1 Example 118.9 Example 2 21.7 Example 3 21.9 Example 4 21.2 Example 5 20.0 Example6 16.5 Reference 14.1 example 2

Among them, in the examples 2 to 5, the brightness change rate exceeded20%, and the difference of the degree that can be identified with thenaked eye was observed compared with the examples 1 and 6 and the like.That is, a conclusion that the display brightness could be improved whenthe relative refractive index nr1 satisfied the relationship of0.91≦nr1≦1.08 was obtained.

[Supplementary Explanation]

Other than the examples described above, as a result of the sameevaluation performed by variously changing the preparation conditions ofthe conductive sheet 11, the following findings were obtained.

(1) The material of the transparent base 12 was not limited to PET, andthe same experimental result was obtained regardless of the material ina range satisfying the relationship of the relative refractive indicesnr1 and nr2 described above. In addition, even if the second protectivelayer 26 b was formed of a different material from the first protectivelayer 26 a, the experimental result was the same in the range satisfyingthe relationship described above.

(2) The effect of reducing the granular feeling of noise was obtained bysetting one of the relative refractive indices nr1 and nr2 to 0.86 orhigher and 1.15 or lower. In addition, the noticeable reduction effectwas obtained by setting both the relative refractive indices nr1 and nr2to 0.86 or higher and 1.15 or lower.

(3) The effect in which the amount of light emitted to the outsidethrough a display screen, that is, the display brightness was improvedwas obtained by setting one of the relative refractive indices nr1 andnr2 to 0.91 or higher and 1.08 or lower. In addition, the noticeableimprovement effect was obtained by setting both the relative refractiveindices nr1 and nr2 to 0.91 or higher and 1.08 or lower.

(4) Even if the conductive sheet 11 was disposed in a state where thetop and bottom surfaces were reversed, approximately the same evaluationresult as described above was obtained.

(Relationship Between Irregularity and Visibility)

In the following Table 4, results of individual evaluations of moire,feeling of roughness, and color noise and an overall evaluation for thesamples according to the examples 7 to 13 and the reference examples 3and 4 are shown.

TABLE 4 Second evaluation Feeling value of Color Overall EV2 [μm] Moireroughness noise evaluation Reference 11 C A B C example 3 Example 7 15 BA B B Example 8 20 B A B B Example 9 26 A A A A Example 10 31 A A A AExample 11 36 A A A A Example 12 48 A B A B Example 13 65 A B A BReference 80 A C A C example 4

Regarding moire, the evaluation an the reference example 3 was C, and itrevealed that moire was noticeable. In addition, the evaluations in theexamples 7 and 8 were B, and moire was recognized but was at a levelcausing no problems. Further, the evaluations in the examples 9 to 13and the reference example 4 were A, and no moire was generated.

Regarding the feeling of roughness, the evaluation in the referenceexample 4 was C, and it revealed that the feeling of roughness wasnoticeable. In addition, the evaluations in the examples 12 and 13 wereB, and the feeling of roughness was recognized but was at a levelcausing no problems. Further, the evaluations in the reference example 3and the examples 7 to 11 were A, and the feeling of roughness was notcaused.

Regarding color noise, the evaluations in the reference example 3 andthe examples 7 and 8 were B, and color noise was recognized but was at alevel causing no problems. In addition, the evaluations in the examples9 to 13 and the reference example 4 were A, and no color noise wasgenerated.

Regarding the overall evaluation, the evaluations in the referenceexamples 3 and 4 were C, and the visibility of the display screen waspoor. In addition, the evaluations in the examples 7, 8, 12, and 13 were8, and any uncomfortable feeling was sensed but the level of thevisibility was sufficient. Further, the evaluations in the examples 9 to11 were A, and the visibility of the display screen was good.

Thus, it was confirmed that, for the centroid position distribution C ofeach opening 18 (or each mesh shape 22) of the mesh pattern 20, bysetting the root mean square deviation of the centroid positions Pc1 toPc9, which were disposed along the reference axis 430 (X′ axis), withrespect to the crossing axis 432 (Y′ axis) to 15 μm or more and 65 μm orless, the generation of moire, feeling of roughness, and color noisecould be suppressed.

It is needless to say that this invention is not limited to theembodiments described above and can be freely modified without departingfrom the gist of this invention.

For example, a program for producing a conductive sheet that causes acomputer to operate in accordance with each function of the apparatusfor producing the conductive sheet described in each embodiment of thepresent invention and a program for producing a conductive sheet thatcauses a computer to execute each step of the above-described method forproducing the conductive sheet as a procedure are other embodiments ofthe present invention. Further, a computer-readable storage medium onwhich such a program is recorded is also one embodiment of the presentinvention.

What is claimed is:
 1. A conductive sheet, comprising: a base; and a conductive portion that is formed on at least one main surface of the base and is formed from a plurality of thin metal wires, wherein a mesh pattern in which different mesh shapes are arrayed in plan view is formed by the conductive portion, and the mesh pattern is configured such that, in a power spectrum of a two-dimensional distribution of centroid positions of the mesh shapes, an average intensity on a higher spatial frequency band side than a predetermined spatial frequency is larger than an average intensity on a lower spatial frequency band side than the predetermined spatial frequency.
 2. The conductive sheet according to claim 1, wherein the predetermined spatial frequency is a spatial frequency at which visual response characteristics of human are equivalent to 5% of a maximum response.
 3. The conductive sheet according to claim 2, wherein the visual response characteristics of human are visual response characteristics obtained based on a Dooley-Shaw function at a distance of distinct vision of 300 mm, and the predetermined spatial frequency is 6 cycles/mm.
 4. The conductive sheet according to claim 1, wherein the predetermined spatial frequency is a spatial frequency at which a value of the power spectrum is maximized.
 5. The conductive sheet according to claim 1, wherein, in a two-dimensional distribution of the centroid positions, a root mean square deviation of the centroid positions which are disposed along a predetermined direction with respect to a direction perpendicular to the predetermined direction is equal to or greater than 15 μm and equal to or less than 65 μm.
 6. The conductive sheet according to claim 1, wherein each of the mesh shapes is a polygonal shape.
 7. The conductive sheet according to claim 6, wherein each of the mesh shapes is determined in accordance with a Voronoi diagram based on a plurality of positions in a planar region.
 8. The conductive sheet according to claim 6, wherein each of the mesh shapes is determined in accordance with a Delaunay diagram based on a plurality of positions in a planar region.
 9. The conductive sheet according to claim 1, wherein the mesh pattern is formed by arraying the mesh shapes without a space.
 10. The conductive sheet according to claim 1, wherein the mesh pattern includes repeated shapes.
 11. The conductive sheet according to claim 1, wherein the conductive portion includes a first conductive portion, which is formed on one main surface of the base and is formed from a plurality of thin metal wires, and a second conductive portion, which is formed on the other main surface of the base and is formed from a plurality of thin metal wires, and the mesh pattern is formed by combining the first and second conductive portions.
 12. The conductive sheet according to claim 11, further comprising: a first protective layer that is provided on the one main surface and covers the first conductive portion; and a second protective layer that is provided on the other main surface and covers the second conductive portion, wherein a relative refractive index of the base with respect to the first protective layer and/or a relative refractive index of the base with respect to the second protective layer are equal to or greater than 0.86 and equal to or less than 1.15.
 13. The conductive sheet according to claim 11, further comprising: a first dummy electrode portion that is formed on the one main surface and is formed from a plurality of thin metal wires electrically insulated from the first conductive portion, wherein the first conductive portion includes a plurality of first conductive patterns which are disposed in one direction and to which a plurality of first sensing portions are respectively connected, the first dummy electrode portion includes a plurality of first dummy patterns disposed in an opening portion between the first conductive patterns adjacent to each other, and a wiring density of the first dummy patterns is equal to a wiring density of the first conductive patterns.
 14. The conductive sheet according to claim 1, wherein the conductive portion is formed on one main surface of the base.
 15. A touch panel comprising: the conductive sheet according to claim 1; and a detection control unit that detects a contact position or a proximity position from a main surface side of the conductive sheet.
 16. A display device, comprising: the conductive sheet according to claim 1; a detection control unit that detects a contact position or a proximity position from one main surface side of the conductive sheet; and a display unit that displays an image on a display screen based on a display signal, wherein the conductive sheet is disposed on the display screen with another main surface side facing the display unit.
 17. A method for producing a conductive sheet, comprising: a generation step of generating image data representing a design of a mesh pattern in which different mesh shapes are arrayed; a calculation step of calculating an evaluation value, which quantifies a degree of variation of centroid positions of the mesh shapes, based on the generated image data; a determination step of determining a piece of the image data as output image data based on the calculated evaluation value and predetermined evaluation conditions; and an output step of obtaining a conductive sheet, in which the mesh pattern is formed on a base in plan view, by outputting and forming a conductive wire on the base based on the determined output image data.
 18. A computer-readable recording medium that records a program causing a computer to execute as a procedure: a generation step of generating image data representing a design of a mesh pattern in which different mesh shapes are arrayed; a calculation step of calculating an evaluation value, which quantifies a degree of variation of centroid positions of the mesh shapes, based on the generated image data; and a determination step of determining a piece of the image data as output image data based on the calculated evaluation value and predetermined evaluation conditions.
 19. The recording medium according to claim 18, wherein, in the calculation step, the evaluation value is calculated based on a power spectrum of a two-dimensional distribution of the centroid positions.
 20. The recording medium according to claim 18, wherein, in the calculation step, in a two-dimensional distribution of the centroid positions, a statistical value of the centroid positions, which are disposed along a predetermined direction, with respect to a direction perpendicular to the predetermined direction is calculated as the evaluation value. 